Dich Chuong 7 IP WDM

8/9/2019 Dich Chuong 7 IP WDM

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MC LC

MC LC ........................................................................................................................................1DANH SCH HNH NH .............................................................................................................. 2......................................................................................................................................................... 2

Chng 7. THUT LU LNG IP/WDM ................................................................................. 37.1 K Thut lu lng IP trn WDM l g? .............................................................................3

7.2 M hnh k thut lu lng IP trn WDM .......................................................................... 47.2.1 K thut lu lng chng ln .........................................................................................47.2.2 K thut lu lng tch hp............................................................................................57.2.3 So snh hai m hnh........................................................................................................6

7.3 C cu chc nng k thut lu lng IP over WDM .......................................................... 77.3.1 C s d liu thng tin trng thi mng IP/WDM ....................................................... 107.3.2 Qun ly giao tip IP ti WDM ......................................................................................127.3.3 V d v chuyn i trng thi ti cu hnh..................................................................127.3.4 Gim st v o lng lu lng...................................................................................147.3.5 Gim st cht lng tn hiu quang ..............................................................................20

7.4 M hnh ha lu lng...................................................................................................... 21

7.4.1 M hnh lu lng d liu v thoi truyn thng........................................................217.4.2 Cc m hnh lu lng d liu : ...................................................................................227.4.3 Mt m hnh d bo bng thng ...................................................................................23

7.5 K thut lu lng MPLS .................................................................................................297.5.1 S cn bng ti :............................................................................................................297.5.2 S cung cp mng: ........................................................................................................34

7.6 Cu hnh li kin trc o ng quang ..............................................................................357.6.1 Cu trc o bnh thng v bt bnh thng ................................................................377.6.2 Trnh by vn thit kt cu trc mng ..................................................................... 387.6.3 Cc thut ton heuristic ................................................................................................ 39

7.7 Cu hnh li cho mng chuyn mch gi WDM ................................................................46

7.7.1 Tng quan v cu hnh li chuyn mch gi WDM ....................................................467.7.2 iu kin cu hnh li ...................................................................................................497.7.3 Mt trng hp nghin cu ..........................................................................................507.7.4 7.7.4 M t thut ton Heuristic ................................................................................... 517.7.5 Tho lun v Heuristic ..................................................................................................587.7.6 Cu hnh li ng quang di c....................................................................................59

7.8 M phng vic ti cu hnh mng IP/WDM: .....................................................................617.8.1 Pht sinh lu lng: ......................................................................................................627.8.2 Kt qu m phng: ........................................................................................................62

7.9 Thit k phn mm k thut lu lng IP/WDM: .............................................................687.9.1 Kin trc phn mm cho m hnh k thut lu lng chng ln: ................................687.9.2 Kin trc phn mm cho m hnh k thut lu lng tch hp: ...................................717.9.3 K thut lu lng IP n giao thc iu khin mng (IP TECP) ...............................727.9.4 Giao din ngi dng- mng IP/WDM (UNI)............................................................. 777.9.5 K thut lu lng WDM n giao thc iu khin mng (WDM-TECP): ................817.9.6 Cng c k thut lu lng IP/WDM ..........................................................................88


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DANH SCH HNH NH


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Chng 7. THUT LU LNG IP/WDM

7.1 K Thut lu lng IP trn WDM l g?

K thut lu lng IP over WDM nhm s dng hiu qu ti nguyn IP/WDM

(v d, cc b nh tuyn IP, b im in, chuyn mch WDM, si quang v cc

bc sng quang) truyn cc lung a ch v cc gi tin. K thut lu lng IPover WDM bao gm k thut lu lng MPLS v k thut lu lng WDM (xem

hnh 7.1)

K thut lu lng MPLS gii quyt vn phn b lung v thit k ng

nhn. Dng iu khin ng i MPLS, k thut lu lng MPLS cung cp cn bng

ti trn mt ng IP topo logic hin ti. MPLS LSP lm vic nh cc ng o dng

chung ti nguyn vi cc IP topo logic c. K thut lu lng WDM gii phng

cc gi nh IP tnh trong mng WDM. K thut lu lng WDM thc hin sao chp

cc pht sinh ca thit k ng quang v chuyn sang IP topo logic. Trong ti cu

hnh mng WDM k thut lu lng MPLS v WDM lm vic cc lp khc nhau,

mt l cho lp IP v lp khc cho WDM. Trong cc mng chuyn mch gi quang, k

thut lu lng WDM v MPLS c th c thc hin hoc l phng php chng ln

hoc phng php tch hp. Ging vic bao ph lp IP trn mng WDM ti cu hnh

(mt phng d liu), ni cc ng o MPLS LSP c phn nh thit lp knhnh sng WDM. Cc ng quang cu trc phn b cc lung vo cc ng quang

v chuyn tip lu lng trong m hnh tch hp. Chng ny chng ta trnh by k

thut lu lng MPLS v WDM.


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Hnh 7.1 K thut lu lng IP/WDM

7.2 M hnh k thut lu lng IP trn WDM

K thut lu lng IP trn WDM c th chia ra hai m hnh: k thut lu lng

chng ln v k thut lu lng tch hp. vi k thut lu lng chng ln IP/WDM

th c mi m un k thut lu lng cho mi lp IP v lp WDM, vic vn hnh

trong mng c th thc thi c lp vi nhau ti mi lp. Gii php k thut lu lng

pht trin hoc cho mng IP hay mng WDM c th p dng trc tip cho mi lp

tng ng. Mng theo m hnh chng ln Server-Client l s phi hp nhp nhng v

thc hin yu cu ca k thut lu lng chng ln. vi k thut lu lng tch hp,

ti u cht lng theo phng din la chn cc mc tiu tham chiu cho c hai

thnh phn mng IP v WDM. Vic ny s yu cu s phc tp ca phn cng cc

thit b thc hin cc chc nng tch hp IP v WDM trn cng mt thit b mng.nhng k thut lu lng tch hp c th thc hin mt cch hiu qu hn

7.2.1 K thut lu lng chng ln

Nguyn l ca k thut lu lng chng ln l k thut lu lng theo mi lp

ti mt thi im. c ngha mt gii php ti u trong khng gian a chiu c tm

bi s tm kim lin tc cho cc chiu khc nhau. Nn gii php ti u l tm kim

tun t-ph thuc v khng m bo c ti u ton cc.

Hnh 7.2 K Thut lu lng chng ln (Overlay Traffic Engineering)

u im ca k thut lu lng chng ln l cc c ch c th an xen t

yu cu tt nht ti mi lp ring bit. (IP hoc WDM) cho cc mc tiu la chn.Hnh 7.2 minh ha k thut lu lng chng ln.


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K thut lu lng chng ln c th c xy dng bng cch kt ni cc b

nh tuyn IP n mt b kt ni cho OXC trn mng WDM thng qua mt b

OADM. Mng IP/WDM xy dng theo cch da theo cc OXC-based WDM, lp my

ch to ra iu kin thun tin kt hp cc thit b quang vi cc si quang. Mi si

quang truyn ti nhiu bc sng m vic nh tuyn cc bc sng ny th c cu

hnh linh hot. Lp my khch (Client layer) c hnh thnh bng cc b nh tuyn

IP c kt ni bng cc ng quang gn trong mng vt l. Tnh topo ca mng o

l c th ti cu hnh do tnh cht c th ti cu hnh cc ng quang ti lp my ch

(Server layer) cc giao tip ca mt b nh tuyn kt ni ti OADM l cc giao tip

c th ti cu hnh c. iu ny c ngha cc a ch IP ln cn kt ni thng qua

cc giao thc c th ti cu hnh c th c thay i bng cch cp nht cc cu hnh

ng quang lp di. Trong cc mng IP/WDM, iu khin tc nghn khng ch

c gii phng mc lung s dng cng mt mng topo logic m cn mc topo

logic s dng ti nguyn v ti cu hnh ng quang. V vy, khng ch ti nguyn

lu lng iu chnh cc gi tin trc khi gi ti mng m mng cng phi iu chnh

tng thch vi cc mu lu lng c la chn theo thang thi gian. Ti lp IP,

iu khin phn nh c s dng qun ly ti nguyn mng (nh bc sng) v

phn b ti cc tuyn IP o. iu khin phn b lp WDM c th l tnh, c nh ti

lc bt u yu cu kt ni, hoc c th phn b ng v thay i theo thi gian ktni. n cng c th linh ng cho php lp WDM cung cp cc kt ni vi cc QoS

khc nhau.

7.2.2 K thut lu lng tch hp.

Nguyn l ca k thut lu lng tch hp l ti u c thc hin ti c hai

mng IP v mng WDM mt cch ng thi. c ngha l gii php ti u c tm

kim trong mt khng gian a chiu. K thut lu lng tch hp c ng dngtrong cc chc nng ca lp IP v lp WDM c kt hp ti mi thit b mng.

Khi chc nng lp IP v lp WDM c tch hp, mt mt phng qun ly v iu

khin tch hp WDM c xem xt cng nhau. Hnh 7.3 m t k thut lu lng tch

hp.


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Hnh 7.3 K thut lu lng tch hp

7.2.3 So snh hai m hnh.

S quan h gia ti u cht lng v phn b ti nguyn phn bit theo phng

php chng ln v phng php tch hp. Vi k thut lu lng chng ln th ti u

cht lng nh cn bng ti v nh tuyn lu lng c th thc hin ti lp IP v n

tch bch ring bit vi phn b ti nguyn vt ly WDM c thc hin ti lp WDM.

Bi v ti u cht lng lp IP c th s dng ti cu hnh cng nh cc c chtruyn thng m khng lin quan ti ti cu hnh. Khi vic ti cu hnh khng lin

quan, c ngha ti u cht lng c tm kim trong tp ti nguyn c nh (cho IP

topo logic c nh). Khi ti cu hnh c s dng vic phn b ti nguyn ng cho

cc topo logic o c bao hm. Sau ti u cht lng lp IP c mt la chn l

bao nhiu ti nguyn cn thit xem xt cc trng thi ca lp WDM, ni ti nguyn

thc s ang chim d.

Mt khc, Ti u cht lng v phn b ti nguyn mng c kt hp vi nhau

ti k thut lu lng tch hp, nu ti u cht lng lin quan n cc ti nguyn

mng thay i th phn b ti nguyn c thc hin t ng v bao gm c ti u

cht lng.

M hnh k thut lu lng c th trin khai theo m hnh phn b hoc tp

trung, Bng 7.1 Ch ra 4 chn la trin khai ca m hnh k thut lu lng (TE) , Vi

m hnh chng ln, v trc gic m hnh c th trin khai theo kiu tp trung hoc

kiu phn b.Ttrong c mt lp IP TE v mt lp WDM TE.


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Khi hai lp TE thng tin cho nhau thng qua giao din bin UNI ca WDM hoc

giao tip gia IP NMS v WDM NMS. Trong cch trin khai chng ln tp trung th

qun ly lp IP trung tm NC&M v qun ly lp WDM trung tm NC&M thu thp cc

thng tin trng thi v cc lp tng ng ca n. Tuy nhin, phng php ny c th

khng cn bng bi v d dng thy l c th tc nghn c nt chai xy ra ti c hai

tng qun ly IP v WDM. Phung php tch hp sp xp mt cch t nhin ti mt

trin khai m hnh phn b cho k thut lu lng. l mi v tr (site) c kh nng

iu khin tc nghn v thc thi quyt nh phn b ti nguyn da theo thng tin

trng thi h thng IP/WDM ni b. K thut lu lng trin khai phn b lm tng

tnh sn sng v tnh linh hot nhng phi thc hin vn ng b phc tp do cc

quyt nh xy ra song song ti cc v tr phn b khc nhau.

Bng 7.1 Trin khai m hnh KTLL

M hnh chng ln M hnh tch hp

Trin khai tp trung KTLL Chng ln tp trung KTLL Tch hp tp trung

Trin khai phn b KTLL Chng ln phn b KTLL Tch hp phn b

Tm li, phng php chng ln c th khng thc hin hiu qu khi kch thc

mng tng ln v c hai my ch NMS l IP v WDM u c th b nghn c nt chai,cn trong m hnh tch hp th phi thc hin trin khai vi s lng ln v phc tp.

s ng b trong mt mng ln gia cc nt mng ca IP/WDM theo thng tin trng

thi mng v thng tin cu hnh phi xem xt theo thi gian ng b vi nhau. S

la chn m hnh k thut lu lng chng ln hay k thut lu lng tch hp v cc

phng thc trin khai l s la chn mt cch ph thuc vo mng vn hnh v lu

lng ng dng. Tuy nhin, C cu chc nng ca k thut lu lng th hin bao

hm hai m hnh ca hai phng php thc thi. Cc thnh phn trong cng mt c cu

l chung cho cc ng dng k thut lu lng trong mng IP/WDM.

7.3 C cu chc nng k thut lu lng IP over WDM

C ch nn tng trong c cu k thut lu lng l ng quang v ng o

cung cp theo yu cu. Tnh cht duy nht trong mng WDM l kh nng ti cu hnh

ng quang v ng o topo logic. l, theo ng quang topo logic vt ly, th

mng vt ly WDM c th h tr mt s lng cc ng topo logic o thit lp bi

cc ng quang.


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Hnh 7.4 ch ra chc nng c bn ca cc thnh phn trong k thut lu lng v

s chuyn i trng thi ti cu hnh bao gm nh sau:

Hnh 7.4 Cu trc khung chc nng ca k thut lu lng IP/WDM

Gim st lu lng(IP Traffic Monitor): Thnh phn ny chu trch nhim thuthp thng k lu lng t cc b nh tuyn/ chuyn mch hoc cc tuyn. h tr

c cu k thut lu lng, Mng IP/WDM gim st lu lng IP.

Phn tch lu lng(Traffic Analysis): Thnh phn ny c s dng thu

thp thng k cho thc thi quyt nh, trong trng hp c cp nht th mt bng bo

co phn tch c to ra.

D on bng thng(Bandwidth Demand Projection): Thnh phn ny s dng d on yu cu bng thng trong tng lai gn da trn o lng trong qu kh

v hin ti v c tnh lu lng.

Gim st cht lng tn hiu(Signal Performance Monitor): thnh phn ny

chu trch nhim quan st QoS ca tn hiu quang cho cc knh bc sng. QoS ca

tn hiu th hin dng phc, l h s ng trn bc sng nh tuyn v qun ly li.

Qun ly li WDM th khng cp trong c cu k thut lu lng ny, v vy QoS

tn hiu ch s dng bi ti cu hnh.


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Chuyn i trng thi ti cu hnh(Traffic-engineering reconfiguration trigger):

Thnh phn ny bao gm cc c ch quyt nh khi ti c cu mc mng c

thc thi. V cng da trn iu kin lu lng, d on bng thng v cc pht sinh

vn hnh,

Thit k topo logic cho ng quang(Lightpath topology design): Thnh phn

ny tnh ton topo logic mng da trn o lu lng v d on bng thng, c th

xem nh ti u th ( b nh tuyn IP c kt ni bng cc ng quang trong lp

WDM) cho cc mc tiu khc nhau (v d: maximize throughput) theo s cng p

cho mt ma trn yu cu cho trc (VD: Mc nt, dung lng giao tip). Tm kim

th ti u c th tng chi ph, thi gian. V ti cu hnh chuyn i trng thi theo

cc mu lu lng, nn cc th ti u s khng tn ti trong khong thi gian di

khi vic ti cu hnh hon tt.Trong thc t tip cn s dng thut ton t tm kimtp trung vo mc tiu ring bit c hiu qu cao, hi t nhanh, v nh hng nh

vo lu lng n thay v ti u ton cc.

S chuyn tip topology (Topology Migration): Thnh phn ny bao gm cc

thut ton nh trnh chuyn tip mng t topo logic c sang topo logic mi. Cho

d cc ti nguyn lp WDM c h tr mi chui chuyn tip, th vn c cc

pht sinh khc lin quan n chuyn tip. v d: vic sp xp ti cu hnh WDM vi

cc knh c dung lng ln. (v d: ti OC-192 trn bc sng) thay i phn nh

ti nguyn c nh hng nghim trng ti s lng ln lu lng u cui. mt th

tc chuyn tip bao gm mt chui s thip lp v gii ta theo cc ng quang

WDM ring bit, cc lung lu lng phi tng thch vi cc thay i ng quang

trong qu trnh v sau mi bc chuyn tip.

Ti cu hnh ng quang(Lightpath reconfiguration): Thnh phn ny c s

dng ti cu hnh cc ng quang khc nhau, v d ly ra v thit lp. N s yu

cu ngc li t cc modun sau:

Thut ton nh tuyn ng quang c dng tnh ton ng quang. Khi

mt l trnh ca ng quang khng c ch nh, thnh phn ny s tnh ton l

trnh ng quang. Nu mt giao thc nh tuyn c sn (v d: OSPF vi s m

rng quang) th ng nh tuyn c th thc hin t bng nh tuyn ni b.

C ch thit lp v gii phng ng kt ni l cn thit v d nh i vi cc

giao thc bo hiu.


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Qun ly giao tip l chu trch nhim cho mt giao tip v cp nht cc thng tin

lin quan. Ti cu hnh ng quang c th c ti n nh cho giao tip khch

WDM ti mt ng quang khc m n s nh hng giao tip WDM ti mng IP.

nh tuyn IP yu cu a ch IP v s cho php chuyn tip gi tin ch trong mt IP

subnet. Topo logic mi c th yu cu thay i a ch giao tip IP.

7.3.1 C s d liu thng tin trng thi mng IP/WDM

Mt c s d liu thng tin trng thi mng c yu cu iu khin v qun

ly mng IP/WDM. Da vo m hnh k thut lu lng v phng thc thc thi c s

d liu thng tin trng thi mng c xy dng v duy tr tng ng. V d, vi

phng thc thc thi l tch hp th mt c s d liu tch hp IP/WDM c duy tr

mi site v c ng b gia cc sites c giao thc phn b thc hin. trong

phng thc chng ln c s d liu IP c lu tr ring bit vi c s d liuWDM.

Thng tin trng thi mng cho k thut lu lng xem xt theo hai phng din:

Ti nguyn v mc s dng. biu th truyn thng ca cc ti nguyn mng

theo mc ch nh tuyn gi c th c thng tin topo logic mt cch n gin. Tuy

nhin, k thut lu lng yu cu thng tin nhiu hn, v d: ton b bng thng v

hiu sut s dng hin ti trn mi tuyn. C hai tng nh tuyn tn ti trong mngchng ln IP/WDM, mt l nh tuyn ng quang cho sang mng vt ly v mt l

nh tuyn d liu thng qua cc ng quang. K thut lu lng c th c thc

thi c hai tng, k thut lu lng WDM quan tm khng ch cc trng thi s dng

ti nguyn mng m cn cc c tnh quang ca cc kt ni quang WDM v cht

lng tn hiu. khi k thut lu lng chng ln thc thi, cc chc nng mc tiu ti

cc lp khc nhau c th s khc nhau. Trong trng hp k thut lu lng tch hp

iu khin lu lng v phn b ti nguyn c xem xt cgn nhau cc mc tiu

ti u phi c phi hp.

D cc m hnh k thut lu lng khc nhau yu cu khc nhau v thit k v

trin khai c s d liu thng tin trng thi mng, nhiu thuc tnh c dng chung

trong hai trng hp s ni sau y. Trong phng php chng ln, c s d liu

thng tin trng thi ca lp IP bao gm thng tin sau:

Topology IP o l mt th c hng cc nh biu th cc b nh tuyn IP v

cc cnh biu th cc ng quang c nhn dng v c yu cu bng mt giao


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thc nh tuyn trng thi chun. Cng bao gm cc tc v dng tn hiu m giao

thc IP c th h tr. Vic ny cn thit cho cu hnh ng.

Trng thi tuyn IP bao gm v dung lng tuyn v kh dng (theo phn

trm). Nhng o lng khc (v d: s lng gi b rt ti mt giao tip ca b nh

tuyn) th c yu cu cc thut ton k thut lu lng, v s bao gm:

ti lp WDM, qun ly mc tiu l mng vt ly ti c th hin bng cc

ng quang. K thut lu lng thc t ti lp ny c m trch bng cch gn

nh x topo logic IP o vo mng vt ly. Vn hnh qun ly mng l phn nh bc

sng v nh tuyn. Nu cc bc sng lin tc th c yu cu theo mt di. Mt

bc sng n phi c n nh, nu thit b mng WDM c kh nng chuyn i

bc sng th cc hop quang khc nhau c th s dng cc bc sng khc nhau. V

vy, Mt c s d liu thng tin trng thi mng lp WDM bao gm cc thnh phn

sau:

Topo logic vt ly l mt biu c hng trn cc nh th hin cc thit b

mng WDM v cc cnh th hin si quang.

Cc c tnh thit b mng ch th kh nng chuyn mch v kh nng s dng

ca cng. Cc thit b mng c th chuyn mch quang ( kt ni tt c cc bc sng

trn cng mt si quang vo n si quang ra c cng cc bc sng). Hoc chuynmch bc sng ( tc l kt ni mt bc sng ring bit trn mt si quang vo ti

cng bc sng trn mt hc nhiu si quang ra). Thm na, Mt tn hiu c th

c chuyn i t ti mt tn s khc thng qua b chuyn i bc sng. Thit b

mng c mt s lng nht nh cc cng xen/rt, v vy c th b tranh chp trn cc

tn hiu xen/rt mt c cu chuyn mch.

Trng thi si quang bao gm mt s cc bc sng, nh hng, loi bo v

tuyn v cht lng tn hiu quang nh tng cng sut bc sng cho si quang. ng

ky bc sng, cng sut bc sng khc nhau, mc tn hiu trn nhiu SNR ca mi

bc sng.

Cc trng thi ng quang bao gm ti nguyn ID thit b mng, ID cng xem,

ID cng rt, ID bc sng, (ca mi hop quang) v cc nh hng, ID si quang, tc

bit, t s tn hiu trn hiu SNR, SRLG (Shared Risk Link Group) ID, cc tu chn

nh: mc u tin ng quang,

Trong k thut lu lng tch hp, topology bc sng v topology si quang

c kt hp vi nhau, s ti u l nh tuyn bc sng theo cng p ca si


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quang, v th, ni dung ca c s d liu lp IP v c s d liu lp WDM trong m

hnh chng ln s c st nhp vo mt c s thng tin trng thi mng IP/WDM.

7.3.2 Qun ly giao tip IP ti WDM

Lm th no cc giao tip iu khin hiu qu gia IP v WDM l cp thit

thc hin k thut lu lng thch hp trong mng IP/WDM. Hin ti, mt giao thcIP n gin c th ch mt ng quang,

Trong min phn mm, IP/WDM yu cu phn mm tng ng qun ly giao

tip phn cng IP trn WDM v dch gia a ch IP v a ch WDM (khi cn thit).

Trong phng thc chng ln c ch gii quyt a ch c yu cu duy tr sp

xp a ch gia hai lp. ch l lp WDM c th s dng i ch IP thay v a ch vt

ly, nhng c cu gii quyt a ch vn cn thit bi v lp IP v lp WDM s dng

hai khng gian a ch khc nhau cho cc trng hp nh tuyn khc nhau, u im

ca phng php chng ln l lm n by cho cc c ch iu khin hin ti ca

mng IP v mng WDM. Trong phng php tch hp, mi giao tip thit b mng

IP/WDM l mt a ch IP, v vy, ch c mt a ch c s dng, v d a ch IP v

c th s dng cho trng hp nh tuyn. Tuy nhin, cc giao thc IP truyn thng

nh OSPF cn c m rng bao hm cc lin quan mng IP/WDM.

7.3.3 V d v chuyn i trng thi ti cu hnh.

Trong hnh 7.5, Ti cu hnh c th c chuyn i bi nhiu h s. V d cc

chuyn i c th bao gm:

K thut lu lng

Li

Bo v/ Khi phc

Bo dng mng


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Hnh 7.5 Ti cu hnh trong mng IP/WDM

Trigger chuyn i trng thi li c pht hin li, phn tch nguyn nhn li,

qun ly li, mi khi li c pht hin v nguyn nhn c xc nh th thit b qun

ly li s bit phi lm g

Thnh phn mng b li c th c cch ly v ti nh tuyn li cc kt ni b

nh hng do li. B chuyn i bo v/D phng c th c s dng h tr khi

phc ng, mi khi mt ng b li, thut ton khi phc c th tnh ton ng d

phng cho ng b tho ra. Vic ny lm nhim v chuyn lu lng ng c bn

sang ng d phng. C ch ti cu hnh cung cp iu kin thit lp v tho ri

cc ng quang. V d trong giao thc bo hiu, giao thc bo hiu phn b ng vai

tr quan trng trong chc nng bo v v khi phc. Bo dng mng bao gm victhay th v vn hnh cc lch trnh c dng ti cu hnh.

C ba thnh phn chnh trong c ch ti cu hnh: thit k topo logic, chuyn i

topo logic, v ti cu hnh ng quang. Thnh phn ti cu hnh ng quang bao

gm ba module: qun ly giao tip, thut ton nh tuyn ng quang v giao thc

bo hiu. Cc c ch ti cu hnh c th b ko theo khi cc iu kin chuyn i trng

thi ph hp.


14/89

7.3.4 Gim st v o lng lu lng.

Cc mng IP/ WDM c dng phn b lu lng IP. o lu lng mng

thng qua gim st IP v cc c ch thu thp cho c cu k thut lu lng, chnh

xc ca o lng trc tip nh hng ti cht lng c cu khung v o lng cung

cp s liu u vo cho k thut lu lng v c m t nh cc iu kin ng ca

mng. Tip theo, x ly lp vng kn, o lu lng mng c th chuyn qua thut ton

ti cu hnh cng nh nh gi hiu lc ca ti cu hnh

Thng k cn thit c thu thp da vo cc mc tiu ti u v thut ton tm

kim ang s dng. v d: Mc lu lng l quan trong khi mc tiu ti u l

throughput ton cc. V tr mt chiu gia hai nt mng l quan trng khi latency

gia hai nt l nh nht.

Ph thuc vo mc tiu k thut lu lng, o lu lng v thng k ti phic la chn cc tp hp gin on mt cch linh ng cho ly mu v o lng.

Cc tp hp ly mu lin quan n c tnh ca cc lung gim st. S sp xp cc

mc ca lu lng c gim st v cng sut x ly ca cc thit b gim st. Cc

mu o lng quyt nh chu k o lng trung bnh ca lu lng. S la chn hp

ly ca cc mc c th gip iu khin hot ng hiu qu ca k thut lu lng, hn

na vic thng k c sn trong giao thc SNMP MIBs,

Tp hp thng k trong khong thi gian di v cc phn tch lin quan l rt

quan trng xc nh mt topo logic mi. Cc yu t chnh ca phn tch ny l tp

hp d liu lu lng ti lp IP i vo thng k ma trn lu lng v cc d bo v

nhu cu lu lng trong tng lai gn.

Gim st lu lng v thu thp thng k khng d dng thc hin do tnh t ph

v lu lng v dung lng cao ca cc trung k internet hin nay, Nu khng xem

xt cn thn, c th cht lng mng s gim nghim trng, hn na cc c lng

ma trn lu lng c th khng c sn theo mi yu cu ca cc b nh tuyn, cc ti

hin c nhng c th khng thng tin c lng mt ma trn hp ly.

Theo [Kali99], th gim st lu lng bao gm cc nguyn tc sau:


15/89

S dng h o tiu chun

o cc c tnh v hng

Dng cc my o chc nng o chnh xc

o lin tc

Cung cp d liu cht lng trong khong thi gian di

Thc hin o t u cui n u cui

Cc cng c v cc phng php gim st lu lng

Kh nng gim st lu lng c th thc thi mc gi hoc mc mng. Chng

ta kho st mt s cng c phn mm gim st lu lng hin c:

Gim st mc gi tin: Phng php ny yu cu gim st tng gi tin, v d: ti

ngun gc gi, mo u gi c th c kim tra v thng tin lin quan c th c

trch ra t mo u. c hai phn mm thng dng gim st gi nh sau:

X tcpdump

Cng c ny c th in ra cc mo u ca gi tin trn giao tip mng v biu din

theo cng thc nh phn (boolean), c th hot ng vi c -w v lu tr cc gi tin

vo mt file phn tch d liu sau ny, v c b c to ra c cc file gi d

liu lu, trong mi trng hp ch cc gi c cc biu thc ph hp th s c x

ly.

tcpdump cng c c -c nu khng c c -c th n lin tc tnh ton cc gi

cho ti khi b ngt bi tn hiu SIGINT hoc tn hiu SIGTERM. Vi c -c n s bt

cc gi n khi b ngt bi tn hiu SIGINT hoc tn hiu SIGTERM hoc mt s

lng gi nht nh c x ly. Cui cng n s bo co s lng gi tin b rt. Vd: do trn b m, v s lng cc gi lin quan ti b lc

X libpcap

y l th vin c th dng bt cc gi trc tip t card mng. Cho php truy

xut c lp thc thi bt cc gi tin bi h iu hnh [Stev98]. ng dng libpcap

c cu trc chung nh sau:

Ch nh giao tip mun tm kim

Khi ng libpcap c th c vn hnh vi nhiu thit b, mi s tm kim

c nhn bit bi mt m t file


16/89

nh ngha quy tc thit lp chi tit cho loi lu lng no mun tm kim, bin

son quy tc v ng dng quy tc thit lp cc phin hoc file

Thc thi vng lp c bn cho s tm kim

ng phin hoc m t file

Gim st mc mng: Phng php ny yu cu gim st mc mng, v d: nghnmng hc nghn c nt chai. Gim st mc mng c th din gii trong 3 cch: o

tch cc, o th ng v gim st iu khin. Phng php o tch cc gi d liu

thng qua mng v quan st kt qu, phng php o th ng xen mt probe vo mt

tuyn ni vi cc node mng, v thu nhn cc thng tin ghi c v lung d liu trn

tuyn; phng thc gim st iu khin bt v phn tch cc thng tin u khin mng

nh thng tin qun ly v nh tuyn mng.

c bit, trong gim st mc mng c th thc hin s dng cng c da vo

Ping, traceroute, SNMP v thit b gim st mng. v d: c th dng Ping o RTT

(tr vng) phn trm mt gi, thi gian p ng thay i v thiu tin cy

Ping-based tools: cng c ny thc thi o v phn tch da vo Ping nh PingER

[Matt00]. Cc cng c Ping-based c th thu thp o tch cc vi cc bn tin ICMP

(echo request/response) nhng cng c ny c 3 thnh phn:

M un gim st v tr: thnh phn ny c lp v cu hnh ti v tr gim st.

D liu Ping c thu thp ti host thng qua HTTP. PingER c th gim st v tr v

cung cp phn tch ngn hn v bo co.

M un gim st v tr t xa: thnh phn ny c lp host t xa th ng, n

lin kt vi t nht mt gim st v tr.

M un thu thp v phn tch v tr: M un thu thp v phn tch v tr c th t

ti mt site n. Hoc mt host n khc. Site thu thp th thu thp thng tin lu

lng t cc site gim st dng HTTP. Chng cung cp d liu c thu thp v phn

tch v cng cho kt qu bo co thng qua Web.

Traceroute: cng c ny in ra cc hop trung gian gia ngun v ch v o lng

tr vng gia ngun v cc hop. Traceroute dng trng IPv4 TTL hoc IPv6 v hai

bn tin ICMP, bt u gi bn tin UDP ti ch vi TTL (hoc gii hn Hop) ca 1,

SNMP: c th dng SNMP thu thp o lng ni b t b nh tuyn IP


17/89

o lng tuyn th ng: phng php ny yu cu cc thit b mng c bit

nh b phn tch giao thc hoc OCX-non. Mn hnh gim st OCX-non l mt rack

lp trn my tnh chy h iu hnh FreeBSD hoc Linux. My tnh c (400Mhz PII,

128Mb RAM, 6-Gbyte SCSI disk) hai card o lng lp vo my tnh, mt b chia

quang dng kt ni gim st mt lung quang OC(155Mbit/s) hoc OC12(622Mbit/s),

DS3, FDDI, v cc giao tip in hin c.

nh ngha flow k thut lu lng

Khi nim flow c dng rng ri nhng vi cc nh ngha khc nhau nh

cung cp QoS, nh tuyn QoS, chuyn tip gi. Mt nh ngha chung ca Traffic

flow trong k thut lu lng l rt quan trong tng hp d liu v s dng thng

k lu lng t cc b nh tuyn ca cc vendor khc nhau cho cc c ch thu thp

lu lng. nh ngha Flow cho o lu lng nh sau:

C hng (Directionality): cc lung (Flow) c th v hng hay hai hng, vi

lung v hng, lu lng t A n B v t B n A xem l cc lung lu lng tch

bit cho mc ch tng hp v phn tch. D liu hai hng cung cp tm nhn n cc

giao thc theo cc cch khc nhau. Bao gm cc vn chng t biu th trong h

thng ng trc chnh, nhng li kh c nhn dng ti cc im u cui. Vy, d

liu hai hng l phc tp v lm cho thut ton k thut lu lng phc tp hn. n gin, c th gi nh cc lung hai hng c phn bit s khc nhau gia hai

lung v hng ca d liu trn cng mt cp node mng. V d mc lu lng v

mc s dng trn mt lung hai hng n gin s l mc lu lng ln v

mc s dng cao ca hai lung v hng. Hoc c th n gin mt lung hai

hng xem nh mt lung v hng v vy lung hai hng gi nh cc lu lng

gia cc cp node mng l lun lun i xng.

im kt cui lung(Flow endpoints): tiu chun nn tng cho cc c tnh ca

lung l cc im kt cui lungflow endpoints m c m t l s thng tin gia

cc thc th mng. Lung c th xem nh l lu lng gia:

Cc ng dng (Applications): c nhn bit bi nhn dng giao thc, cng

ngun, a ch IP ngun, cng ch, a ch IP ch

My ch (host): Nhn bit bi a ch IP ngun, a ch IP ch

Cc mng (Networks): Nhn bit bi prefix IP ngun, Prefix IP ch.


18/89

Lu lng dng chung mt ng chung trn mng: nhn bit bi giao tip b

nh tuyn vo, giao tip b nh tuyn ra.

Flow granularity: Mi lung c lin kt vi mt granularity c kch thc nh

sau:

Chn mu gim st lu lngTnh hiu qu gim st lu lng lin quan n chn mu gim st lu lng,

c phn bit theo chn mu gim st v chn mu o lng, khi gim st mng, tn

ti s tha hip gia chnh xc ca gim st v thng tin mo u.

C hai phng thc gim st lu lng mng. l t gim st bng cc chc nng

t gim st ca mng v gim st thc hin bi cc thit b chuyn dng khc. Trong

mi trng hp th u khng mnh c thng tin y cho nhim v gim

st mt cch trn vn, v vy gim st phi c a ra bng cc mu th cng, nu

iu ny xy ra th cn phi c mt quy tc iu khin ly mu mc lu lng

lp di c th c c lng tt nht t cc mu thu c ti mt t l kinh t nht

c th chp nhn c.

Mt s thit b o hoc phn cng/chuyn mch c kh nng gim st lin tc

cc lung d liu, cc ng dng nh k hoch dung lng khng yu cu ti mc

chi tit. Trong khi NSFNETera, ANS Communications Inc, a ra vic kim tra ly

mu ti mc 1 trong 50 gi, 1 trong 100 gi v 1 trong 1000 gi, thc hin mc

ch k hoch dung lng th h thy rng tc ly mu ca 1 trong N gi c th

chp nhn c cho cc gi tr khc nhau ca N, nhng tc ly mu ca 1 trong

1000 gi th yu cu khong thi gian tin cy qu cao thit k dung lng. Mc 1

trong N gi l thch hp cho ti cu hnh mc mng. Trong cc mng IP ngy nay, cn

thit phi nghin cu thm, c th c hng trm cch khc nhau cho khi u tt, sau

ly mu c th s c cu hnh bi ngi dng, mt c im quan trng l c th

iu chnh gia mc chnh xc o lng, cc c tnh lu lng v cng sut x ly.

Ly mu theo khong thi gian th kt qu khng phn nh chnh xc c tnh bng

pht ca lu lng

Khi ti cu hnh mc mng th cht lng c nh hng (v d: ti u latency

u cui n u cui) o lng lin quan yu cu cc nhn thi gian (timestemp)

truyn dn/n ca gi chnh xc. Cc phng n ly mu s theo cc yu cu bao

gm:


19/89

Chn ngu nhin 1 trong N gi.

Chn tun t cc gi theo thi gian nghin cu, phn tch cc ln n ca

gi.

Chn mi gi t mt lung n (flow c xc nh t lp cao hn tng

ng)

Mc d nghin cu thm v tc ly mu cho tin cy c th chp nhn c

v khong thi gian ly mu tin cy cho cc yu cu ng dng ring bit. R rng c

hai tnh cht ca gim st lu lng cho mc mng v mc ch ti cu hnh l:

Tc ly mu c kh nng iu chnh c

X ly d liu off-line

Ma trn lu lng v chu k ly mu o lng.

V tn sut ly mu, mc tiu gim st l to ra ma trn lu lng mng theo yu

cu v d an trong tng lai v lu lng, mt lung IP cho ti cu hnh mc mng

bao gm cc dng lu lng n t cc b nh tuyn bin ny n cc b nh tuyn

bin khc. Cc lung c c trng bi theo di theo thi gian s lng byes trn

giy n ti cc lung. theo di thi gian ca dng lu lng c th bao gm trung

bnh cc byte trong dng lu lng trn mt khong thi gian xc nh trc.

Tham s o lng c bn cho ti cu hnh mc mng l ma trn ct lu lng

gia cc b nh tuyn bin trong mng IP/WDM. Thng thng chng ta cn o

VtP(i;j) th hin cc mc lu lng ca lu lng loi P i t b nh tuyn bin

th i n b nh tuyn bin th j trong khong thi gian T, v vy Vic o lng a

ra mc lu lng trong khong thi gian T cho mi cp b nh tuyn bin theo

mi loi lu lng. T l tham s chu k o lng l khong thi gian lp li ca qutrnh theo di lu lng. Cho VtP(I,j) topo logic mng IP v thut ton nh tuyn s

dng, ct lu lng c a cho mi tuyn IP trong mi khong thi gian c th

c xc nh.

V d: dng lu lng c m t l thi gian theo di gm trung bnh 5 pht

mt s byets/s quan st c. chu k thi gian T ly theo trung bnh khong thi gian

quan st.

Theo ly tng, kh gi xut ra kt qu o ca b nh tuyn, cc gi xut ra c

nh du v m t ni dung ca n, cc b nh tuyn c cu hnh vi s cho php


20/89

ca ngi dng ch nh cc trng d liu m h mun xut ra. Bn trong gi c

vit theo cc trng c ch s nhn dng, s dng cc ch s (index)s n gin

ha v linh ng vic thu thp v cung cp trong cc tp hp v kt hp theo yu cu

khch hng. Trong thit k ti cu hnh mc mng th bt mt n c dng o

lng thu thp. mt n s c tham chiu nh l prefix ca mng c trng cho a

ch IP v chiu di mt n mng ca mng ni b trong b nh tuyn bin ring bit.

7.3.5 Gim st cht lng tn hiu quang

C cu khung k thut lu lng thit k mng v topo logic theo yu cu lu

lng cng nh mc s dng ngun ti nguyn v sn sng cng nh QoS ca

tn hiu,Cc c tnh lp quang nh hng ti quyt nh mc mng. V d, QoS c

th gii hn s lng knh bc sng qua mt tuyn quang v tc bit trn cc knh

ny, Hn na, QoS tn hiu quang x ly cc h s ng m khng c trong cc tnhiu in truyn thng. Nu khng xem xt cc c tnh lp WDM th ch mong

khng xy ra hin tng cng p ti nguyn quang no xy ra, mt khi c x ly

topo logic IP o (theo yu cu) c to ra, th gi nh l topology c th lun lun

c h tr s dng cc knh quang. Hn na s tng ln nhanh khi cc tnh ton bi

s nh tuyn ng quang c x ly ng thi cho vic ti u. Trong c cu khung

IP/WDM tch hp cc c tnh WDM quang c kt ni ti cc giao thc iu khin

IP tng thch. Mt mng WDM c th c h thng qun ly li, nhng c tch hp

vo vic iu khin IP, v vy mng IP/WDM tch hp vn cn x ly cc c tnh

chnh ca IP, l tnh tng thch v tnh linh hot.

Mi khi tranh chp mt s c tnh quang phi c xem xt bi cc lp thp

hn (lp1 hoc 2) nhng vn l lm sao phn nh trch nhim cho lp trn hay

lp di v iu khin mng nh th no s lm n by hay t ra cng c nhn bit

bi cc tnh cht lin quan n quang.

Gim st cht lng trong mng ton quang l mt qu trnh tn km chi ph v

yu cu cc b chia quang cho cc thit b c bit hoc cc thit b mng. Tuy nhin,

sau b tch cc tn hiu gc s b gim cht lng v khong cch truyn dn s b

gii hn nu khng c b ti to tn hiu quang. B ti to tn hiu trong min quang

(v d b chuyn i quang transponder) th cha hon thin v rt t tin, v vy

trong thc t, Trong giai on hin nay gim st cht lng cho mng ton quangtrong cc m hnh bc thang vn l vn t pht sinh cha c gii quyt. Trong


21/89

cc h thng quang O-E-O QoS tn hiu t xy ra cc vn ny v ti mi hop tn

hiu quang li c ti to

7.4 M hnh ha lu lng.

C hai giai on trong m hnh ha mt mng truyn thng hay mng my tnh : m

hnh ha lu lng v m hnh ha h thng . Mt m hnh ha lu lng dng m tlu lng vo mt h thng nh l tc lu lng n , phn phi lu lng v s dng

ng ni, y m hnh ha h thng s dng m t h thng mng ca chnh n nh

l kin trc v m hnh hng i . C hai loi m hnh h thng: m hnh h thng mt v

m hnh h thng hng i . Mt m hnh h thng mt trong sut c s dng cho m

hnh cc mng chuyn mch mch m khng c ni ch . V th h thng y ,

khi mt khch hng n s khng c phc v nhng mt . H thng mt p ng da

trn cung cp a ch khch hng cn. . Mt m hnh h thng i trong sut c s dngcho mng chuyn mch gi . y gi thuyt c mt s v hn ni i . V th nu tt c

cc server bn th khi c mt khch hng n s c lu ti mt v tr ni i trong h

thng . Vi m hnh ny th khng c mt khch hng no b mt nhng phi i mt thi

gian nht nh c phc v . M hnh i thit lp kch thc b m v chnh sch

hng i lin quan n a ch khch hng . Trong phn ny tp trung chnh da trn m

hnh ha lu lng .

7.4.1 M hnh lu lng d liu v thoi truyn thng.

Lu lng thoi c m hnh ha s dng m hnh Erlang , chnh l m hnh mt

trong sut. Nu lng lu lng hoc cng lu lng c m t l th s c

tnh theo cng thc sau:

= x h

: tc cuc gi/ khch hng nh: thi gian chim gi trung bnh ca cuc gi.

n v ca cng lu lng gi l erlang ( ERL). Lu lng ca mt erl ngha l

trung bnh mt knh c chim gi . Nghn trong m hnh Erlang tng ng vi mt

cuc gi b mt. C hai loi nghn khc nhau: nghn cuc gi v nghn thi gian. Nghn

cuc gi xy ra khi mt cuc gi tm trn tt c cc knh u b chim gi ti mt thi

im bt k. Chc chn nghn cuc gi BC o QoS tt hn t quan im ca khch hng .Tng cng mt h thng mt MG/n/n c n knh trn ng lin kt , cc cuc gi n x

l theo tin trnh possion vi tc vi tc v thi gian chim gi cc cuc gi l c


22/89

lp tng ng l h, ta c quan h gia nghn cuc gi , cng lu lng v thi gian

chim gi trung bnh ca cuc gi c cho bi Erlang vi cng thc sau:

Lu lng d liu c th c phn phi s dng m hnh hng i . y lu

lng d liu c c trng bi cc thng s: tc gi , chiu di trung bnh ca gi L

v thi gian truyn ti gi 1/ . Tng tc cc ng lin kt h thng l R . V d tng

cc n v d liu trn n v thi gian , thi gian truyn gi c tnh L/R. V th lng

lu lng c th c m t bi ti lu lng nh sau:

T quan im mt khch hng , QoS l mt c trng quan trng . QoS c trnh

by bi PZ, m n c th l mt gi phi i lu hn mt gi tr tham chiu z . Tng mt

h thng M/M/1 , m c gi n phn phi theo tin trnh Possion vi tc v chiu

di cc gi l c lp nhau v phn phi ng nht L, quan h gia ti lu lng , dung

lng h thng v QoS c tnh theo cng thc sau:

7.4.2 Cc m hnh lu lng d liu :

Vo [lela94] lu lng Ethernet LAN c nghin cu ghi li hng trm ca hng

nghn gi Ethernet chnh xc cao bao gm c thi gian n v chiu di gi . Nghin

cu ch ra rng lu lng Ethernet dng nh thay i cc k do c s c mt ca

burstines qua mt thang t l theo thi gian t micro giy n mili giy , giy , pht, gi v

ngy . Thm vo , nghin cu cng ch ra rng lu lng Ethernet th trng thi tng

t nhau . iu ny c ngha l lu lng ging nhau trong tt c cac mc thi gian v c

th s dng mt thng s c trng c bit n l thng s Hurst m t tnh t nhin


23/89

ca lu lng . Cc tnh cht ca lu lng erthernet khng th c nm bt s dng m

hnh lu lng truyn thng nh m hnh Possion.

Vo [Pax95] lu lng mng internet WAN c nghin cu hai mc gi v

o lng kt ni . Nghin cu ch ra rng ti mc gi s phn phi theo kinh nghim ca

thi gian trong cc gi TELET khng tun theo qui lut hm m v ti mc kt ni phin

TELNET tng tc bn trong kt ni theo phn phi ca tin trnh Possion . Tuy nhin

nghin cu cng ch ra rng ti mc kt ni cho cc kt ni vi cc phin khi ng ngi

s dng ( FTP , HTTP) k thut pht kt ni n l burst v thm ch tnh tng quan

khng cn tun theo tin trnh passion.

nm bt c burstnet ca lu lng d liu internet cc phng php phn phi

theo hm m nh :long- normal, Weibull, phn phi Pareto vi v tr v dng thng s

c s dng vi chiu di di ph thuc nhau v qu trnh x l tng t nhau cng nh

phng php Fractional Brownion motion c th c s dng.

7.4.3 Mt m hnh d bo bng thng

K thut lu lng vng kn hot ng theo ch hi tip cng nh d bo bng

thng . K thut lu lng hi tip vng kn c m t trong phn 7.10 . D bo bng

thng c xem l cng c hu dng cho k thut lu lng . Vic tin on bng thng

trong tng li c s dng cho vic khi ng cu hnh lai cp mng . Bng vic tinon bng thng ca lu lng cho php quyt nh c dung lng yu cu ca cc

ng kt ni IP/WDM v quyt nh yu cu cu hnh mng.

Mt dng lu lng IP th cho php khng trc tip ca cc gi IP ( khng ging m

hnh truyn thng ) gia hai im u cui. im u cui c th l hai router k nhau

trong trng hp dng lu lng IP cho php truyn lu lng trn c lin kt gia hai

router . S la chn , cc u cui ca mt dng lu lng c th khng i qua hai router

k nhau . Dng lu lng khng trc tip . iu ny phn nh s khng i xng ca lu

lng gia hai u cui . Khi cho trc mt dng lu lng vi c im ca n v c

lng bng thng ca dng lu lng . Vic c lng bng thng cho php quyt nh

c s ng lin kt IP/WDM cn v cu hnh li mng

Vic tin on mc thi gian bao xa trong tng lai cho mt tin on . Mc thi

gian cho cu hnh li cp mng c quyt nh bi nhiu thng s . Mt trong cch

cu hnh li cp mng l kh nng p ng s thay i ti lu lng trong khong thi

gian ca ngy . Mc thi gian cho php cu hnh li cp ca mng bao gm:

- Thi gian thc hin mt tin on.


24/89

- Thi gian tnh ton cu trc mng mi.

- Thi gian chuyn t cu trc mng c sang mng mi.

Thi gian thc hin cho vic tin on bng thng ph thuc vo tnh ton phc tp

ca m hnh tin on . Thi gian tnh ton cu trc mng mi da vo cc thut ton

phc tp hay l s phng on hiu nng ca vic thit kt cu trc mng . Thi gianchuyn t cu trc mng c sang mng mi ph thuc vo chn la th tc chuyn i .

Vic thc hin chuyn i chc chn phi theo tun t ca thit lp v phn chia cc kt

ni IP/WDM . Trong trng hp thi gian di chuyn bao gm thi gian thit lp v ngt

kt ni cc ng WDM v thi gian cho giao thc nh tuyn n nh cc kt ni sau

mi ln thay i cu trc mng.

T nhng quyt nh trn th mc thi gian cho vic cu hnh li mng l chc chn

v khong thi gian cho vic cu hnh li cp mng hot ng .

Vic tin on bng thng dng lu lng trong gian on tip theo ph thuc vo

nhiu thng s sau:

- Thi gian ca ngy v thi gian ca tun: Chng 3 trnh by r rng v tnh

tng quan thi gian ca ngy vi cc gi tr lu lng .

- Tnh tng quan t xem li cc mu thi gian : Gi thit l gi tr lu lng trong

qu kh gn y s tc ng n gi tr lu lng trong tng lai gn

- Tin trnh lu lng n : tin on bng thng yu cu da vo c im ca

lung lu lng tnh ton.

Tin trnh FBM ( Fractional Brownian motion) : tin trnh FBM c m t bi

ba thng s : tc n trung bnh m, h s variance a, v thng s Hurst H . Mt mng

IP/WDM l m hnh ca tin trnh FBM tnh ton ra gi tr dao ng lu lng nh

trong mt khong thi gian ln . Tin trnh FBM c m t bi cng thc sau:

Z(t) l gi tr x l theo tin trnh FBM c nh ngha nh sau:

- Z(t) : c tng n nh

- Z(0)=0 v E[Z(t)]=0 ti tt c cc gi tr ca t.

- Z(t) c cc ng lien tc .


25/89

- Z(t) phn b theo qui lut gaussian.

Variance ca A(t) c tnh theo cng thc sau :

Xem xt hng i i vi tin trnh n FBM vi tc dch v C khng i . H

thng ny c bn thng s : m l tc trung bnh , a l h s variance ca tin trnh n ,

H l thng s Hurst . C l tc dch v . Kh nng trn hng i trn v d P(Q>B)

y B l kch thc b m c tnh theo cng thc sau:

Mt yu cu kh nng trn b gii ni v d:

Tc dch v ca hng i C c m t theo cng thc sau:

Cc nguyn tc d bo lu lng:

Nguyn tc u tin l lu lng bng thng trong thi gian ti ph thuc vo

mnh lu lng quan st dng lu lng vo cc thi im trong tun .

Nguyn tc ny phn nh mc tp trung gi tr lu lng thi gian trong ngy ,

thi gian trong tun kt hp gim st dng lu lng trn cc ng kt ni . y c

lng mt bt u tin gi tr lu lng trung bnh trong thi gian ti ging gi tr lu

lng cng thi im trong ngy hay trong tun . iu ny c tnh theo cng thc:

F[h,d] l gi tr lu lng quan st c trong h gi ca ngy v d l gi lu lng

trong tun . Vi tc pht trin ca gi tr lu lng t tun ny n tun khc c m

hnh ha bi thng s . Do tc lu lng tng theo hm m nh sau:


26/89

Gi tr c c lng bng cch o lu lng . Gi W0, W1 l tng lu lng quan

st c trong hai tun da trn cc dng lu lng . c xc nh theo cng thc:

Nguyn tc th hai l tin on bng thng lu lng trong thi gian ti s

khc t vic gim st lu lng tht ging vi cch m thc hin trc y

. A ( h-1) gi tr lu lng tht o c ti thi gian h-1 . F(h-1) l gi tr lu

lng tin on ti khong thi gian h-1 ta c:

L t l tnh ton th hin s khc nhau gia gi tr lu lng tin on v gi tr lu

lng thc t o c . y :

Gi tr c chn thch hp sao cho sai s gia gi tr lu lng o c

L nh nht cho phn d liu qu kh c chn nh nht l :

Hay:


27/89

Vi mt tin trnh FBM vi tc trung bnh F2, v kch thc b m ca router l

B v gii hn ca kh nng mt gi l khi dung lng yu cu t c:

y:

Hai phng php m t lu lng pha trn c lng hai thng s a v H t vic

o lu lng . Phng php th nht ch ra rng o gi tr lu lng cho mi khong nh

thi gian trong N ln trong khong thi gian th i l T(i) . Ga tr lu lng trung bnh c

lng c l m^ t c:

Ga tr c lng variance V^t :

Php o c tp trung cho k nhm khng kha vi kch thc kt v t c gi tr

variance V^kt . c lng hai gi tr variance V^t v V^kt tnh c gi tr a v H.

Trong phng php th hai , thng s H c c lng bng cch v th hin thi

gian variance. Cho mt khong nh thi gian X k , k=1,2, ...., . Ta xy dng tp trung m

mu c gi tr X(m)kc tnh :

y nu ta v logV[X(m)k] ngc li logm kt qu hnh v -2(1-H^), H^ l c

lng ca H.


28/89

Cc thng s m hnh :

Cc thng s c trng cho m hnh d on bng thng :

- Kch thc ca khong thi gian croase-grained: Kt qu ca vic gim st lu

lng trong ma trn lu lng d liu bao gm gi tr lu lng trung bnh qua mt

khong thi gian fine-grained ca ca mt thi im. Kch thc ca khong thi giancroase-grained c s dng t c lu lng trung bnh qua thi gian coarse-gained

bng cch tp hp d liu lu lng fine-grained.

- Kch thc b m router :Kch thc ca b m router c s dng trong m

hnh tin on dung lng ca mt lung d liu.

- Gii hn kh nng mt gi : Thng s ny dng d on bng thng ca mt

lung d liu.

- Cu trc mng, thut ton nh tuyn :Cu trc mng kt hp vi gii thut nh

tuyn gip quyt nh c lung d liu cung cp cho mt lin kt t o dng lu lng

t router bin n router bin.

Vic o thng s lu lng thc hin t route bin fine-grained n ma trn lu

lng router bin. T thng s o c ny , tt c cc thng s khc s c phng on

thng qua n . Cc thng s cho php c tnh ton cho vic cu hnh li ti bt u ca

mi giai on croase-grained :

- Coarse-grained trung bnh cho cc lung lu lng cho mi u vo ra ca router

bin : lu lng coarse-grained c tnh ton t vic o lu lng d liu fine-grained.

- Ga tr coarse-grained trung bnh c tnh O(N2) , trong N l s router bin

trong mng .

- Coarse-grained v fine-grained trung bnh cho gi tr lu lng cung cp cho milin kt khng trc tip : t router bin n ma trn lu lng d liu router bin , kin

trc mng v thut ton nh tuyn , gi tr lu lng cung cp cho mi lin kt c th

c tnh ton cho c giai on coarse-gained v fine-gained .

- phc tp ca tnh ton l O(E2) trong E l s lin kt ( kt ni ) trong mng.

- Cc thng s d on bng thng : F1, F2, F3 cho mi dng d liu , cc thng s d

on bng thng F1, F2, F3 c th c tnh ton t cng thc trn . Tnh ton ny c

thc hin khi bt u ti mi khong thi gian coarse-grained.

phc tp tnh ton l O(N2) vi N l s router bin trong mng


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T khi cu hnh li thm ch thay i cu trc ca mt mng IP , nhiu thng s cn

c tnh ton li sau mt cu hnh li . Trong thc t coarse-gained v fine-gained trung

bnh cho cc dng lu lng ti mi lin kt cn c tnh ton li sau mt cu hnh li .

Cc thng s khng thay i a, H, p v c s dng trong m hnh d on bng thng

v c c nh t vic o lng (tnh ton ) lu lng d liu . Khng thay i mt trong

cc thng s ny cn c tnh ton li mt ln cho mi s kin cu hnh li hay tng thi

k ( v d mt tun mt ln).

7.5 K thut lu lng MPLS

Cc gi d liu c chuyn tng hop-hop da ch n trong phn mo u ca gi

d liu bng nh tuyn ni . Mc ch ca k thut lu lng MPLS l ti u vic tn

dng ti nguyn mng bng vic iu khin chnh xc ni ca cc dng lu lng vi

min nh tuyn ca n . Cc k thut iu khin nh l bo hiu, thng tin ch n vchuyn tip gi c s dng trong k thut MPLS c trnh by trong phn trc

ca chng.

Lin quan n chn la ng k thut MPLS c s dng cho hai mc ch :

- Cn bng ti : c s dng cn bng cc dng lu lng ngang qua mng

trnh nghn , cc im nng v hin tht c chai . c bit vic thit k trch trng hp

cc thnh phn ca mng qu ti trong khi cc thnh phn khc cha s dng ht tinguyn

- S cung cp mng : c s dng mng cung cp ton cu , phng php ti u

l kt qu ca vic qui hoch pht trin mng

7.5.1 S cn bng ti :

Trong mt mng IP ghp nhiu ng c gi tr nh nhau c to thnh t cc nt

mng . Khng c s r rng trong vic nh tuyn hay h tr cn bng ti , mt ngc chn ty . Hnh 7.6 s lm r hn vn nay , tt c lu lng c chuyn

n cng mt ng trong khi cc v tr khc vn cn ri


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Hnh 7.6 Vn fish

d liu n c cc a ch ch nh hnh v. OSPF gii thiu k thut

( Equal-Cost Multiple Paths) , ti c chia ra ghp nhiu ng . Ba phng php

thc hin tch lu lng da trn ghp nhiu ng c gi tr ngang nhau :

Da vo bn tin yu cu gi chuyn n : Phng php ny phn phi cc gi tn

da vo kiu bn tin yu cu cc gi chuyn ti theo nhiu ng ghp . i vi cc bn

tin yu cu ca cc gi chuyn ti c kh nng lm tnh lin kt lu lng v do hiu nng

hot ng ca giao thc TCP km . y phng php ny ch c th p dng khi tr

ca cc ng ghp hu nh ngang nhau.

Phn chia da vo tin t mo u thm vo cc gi ca cc hop sn sng tiptheo :Phng php ny km trong vic c gng gia lin kt lu lng b s tch lu

lng cng vi a ch ch gi tin mo u . Nn phng php ny c p dng trong

mng WAN tc cao nhng cc tin t mo u ngn l vn cn phi gii quyt khi

phn chnh ca lu lng thng c nh sn vi mt tin t n.

Bm n cp ngun v ch : Phng php ny p dng chc nng bm v d s

dng da vo m CRC-16 c p dng cho a ch ngun v a ch ch trong gi d

liu . Khng gian bm c chia ra gia cc ng sn sng bng cch thit lp cc gii

hn hay hiu nng vn hnh ca mt module . Khi lu lng gia cc ngun ging nhau

v cc ch cn li cng ng dn . Phng php ny c p dng cho mng WAN tc

cao.

K thut lu lng MPLS c nhiu im u vit hn so vi EMCP im : th nht

MPLS cung cp vic chn la ng ti u cn EMCP ch c gng phn phi ti trn

nhiu ng c gi tr ngang nhau khng xc nh ti u cc dng lu lng n nhiu

ng cng khng bit c mc sn sng ca dng lu lng v iu kin ti ng

ca nhiu ng . K thut lu lng MPLS thng qua OSPF vi k thut LSA m v


31/89

duy tr mt c s d liu k thut lu lng bao gm thng tin k thut lu lng ng vi

mi lin kt trn tng bng thng , bng thng sn sng bng thng t trc v d tr .

Cng vi c s d liu k thut lu lng , k thut lu lng MPLS cho php to ra mt

lung ti u quyt nh v tr trong mt mi trng mng ng .R rng vic phn phi ti

trn nhiu ng khng phi lun l cch ti u . khong cch mt phn ca mt ng

c gi tr ngang nhau b qu ti trong khi phn khc th lu lng t hoc ang trng

thi ri . Mt thut ton cn bng ti ti u dng ch lung lu lng n nhng ng

sn sng dnh cho n. IETF OSPF OMP(Optimised Multi Path) ngh trin khai LSA

m cho LSA-OMP_LINK_LOAD v LSA_OMP_PATH_LOAD LSA.

LSA_OMP_LINK_LOAD bao gm nhng thng tin sau :

Ti lin kt ca mi hng o l mt phn ca dung lng lin kt.

T l rt gi do trn ti mi hng i trong mi hng.

Dung lng lin kt kilobytes/s

LSA_OMP_PATH_LOAD bao gm nhng thng tin sau :

Ti cao nht trong hng t ngun hng n ch c m t l mt phn ca

dung lng lin kt. Ch ng lin kt vi ti cao nht khng th lin kt vi dung

lng sn sang thp nht .

Tng gi rt trong hng t ngun n ch do trn gi c tnh theo cng thc

sau:

Trong Lpath l t l rt gi cho ng truyn v Llink l t l rt gi cho cc lin kt

trong ng truyn .

Dung lng lin kt nh nht trn ng truyn trong hng t ngun nch .

iu khin chnh xc ng ti ngang nhau , OSPF-OMP nh ngha ti tng

ng v gii hn phn on ti . Ti tng ng c suy ra t vic ghp mt phn ti

hin ti bng mt h s c lng da trn s gim kch thc ca gi m TCP c chp

nhn lm chm xung m khng gy ra tt nghn . Mi khi thit lp cc ng dn vi

ti tng ng cao nht c nh ngha nh l gii hn phn on ti . Thm vo mi ng dn trong cu trc hop tip theo s m bo sn sng: share lu lng, gia tng


32/89

tnh di chuyn, m s di chuyn . Thut ton OSPF- OMP iu chnh ti mi ng dn

theo phng php sau:

Gia tng s di chuyn ng truyn th khng thay i nu ng truyn bao

gm gii hn phn on ti.

Nu ng truyn khng bao gm gii hn phn on ti nhng gii hn phnon ti thay i , th ng truyn ny xem nh bao gm gii hn phn on ti .

ng truyn c iu chnh theo:

- Gia tng s di chuyn: thip lp s gia tng di chuyn thp nht t bt k ng

truyn no bao gm gii hn phn on ti.

- Thit lp s gia tng di chuyn bng mt na gi tr gc ca n.

- Nu ng truyn khng bao gm gii hn phn on ti v hoc l ng truynkhng c xem l bao gm gii hn phn on ti hoc l gii hn phn on ti khng

thay i th gia tng di chuyn.

Hnh 7.7 l v d v cn bng ti s dng thut ton OSPF-OMP m ti router d

lu lng n router c c ct thnh hai ng . p dng chc nng bm cho ngun v

ch ti router d lu lng t a n c th c chuyn n mt ng trong khi lu

lng t b n c c ch nh bi mt ng khc .

Hnh 7.7 OSPF-OMP

So snh vi phng php ECMP , k thut lu lng MPLS cho php tnh ton v

thit lp LSP m c th thay i hon ton hng chuyn tip k nhau. Trong trng hp

lu lng mng thp th vic nh tuyn c quyt nh bng iu khin thi gian tr nh

nht . Trong trng hp ngc li th quyt nh nh tuyn phi xem xt n cc lin ktdung lng thp v cc lin kt ti trng . Bng vic cn bng ti vic s dng mng c

th t c hiu qu ti a . Tuy nhin khi lu lng s dng mng tng ln trong tng


33/89

lai , cn bng ti c iu chnh gi tr lin kt khng cn n gin na bi v khi

mng tin n hay gn vi dung lng ti a . MPLS-OMP(Optimised Multi- Path) s

dng ging nh gii thut cn bng ti trong OSPF-LMP ( Link Management Protocol).

Cha kha khc nhau gia hai gii thut MPLS-OMP v OSPF-LMP l sinh ra trong dung

lng MPLS qu trnh thit lp v gii ta LSP. S gia tng cc mch cng vi s pht

trin ca lu lng , k thut lu lng MPLS hi vng trch c nhng im nng v

nghn t c ti a v hiu qu s dng mng hay lu lng. T quan im tch

hp mt LSP c thit lp mt ln , LSP n u ra tr thnh mt hng xm o v cng

trng thi ti ca n. Nu c nhiu ng gia hai node ( u ra , u vo) th ti s c

tch ra trn nhng ng ny . Nhng ng c ti lu lng thp s c xa trong

chuyn tip k cn.

Hnh 7.8 MPLS-OMP

Hnh 7.8 l mt v d cho vic thc hin cn bng ti s dng gii thut MPLS-

OMP . Ti router d , mt MPLS ng vo router v khi to mt LSP n t router d n

router c . Mt ln LSP thit lp chuyn n hop k tip s c cp nht ti router d router c tr thnh mt hng xm o trc tip ca d. Bng cch thu nhn ng ti LSP ,


34/89

LSP ch c cu hnh mang lu lng gc t node b . Theo nh vy lu lng c

phn phi da vo ti nguyn sn sng v dung lng .

7.5.2 S cung cp mng:

K thut lu lng MPLS c th c s dng cung mng nh l mt k hoch

mng di hn hay ngn hn . Mc d thit lp/gii ta trng thi ng LSP , k thut lulng MPLS c th h tr mt di cc ng dng mng v d mng VPN ng v tnh,

mng LAN o. Vi mc ch ca k thut lu lng , LSP o c thit lp hay xa b

da vo o lng v/hay d n phn phi lu lng. Hai cng vic trong k thut lu

lng MPLS l thit k LSP v xc nh lu lng . Thit k LSP quyt nh ng nh

tuyn v thi ko di s sng ca LSP, y vic xc nh bn lu lng da vo ti

nguyn sn sng ca mng . C hai cng vic thc hin c lp da vo nhng vn ti

u ton hc c in. Thit k LSP c cng thc ha nh l vn ng i ti u. Davo h met v cc i tng ti u , vn ng i ti u c phn vo lp cc vn

ng i ngn nht , vn dung lng ln nht v vn thnh phn ng i v vn

ng i nhanh. Xc nh lu lng da vo nhng vn tnh ton phc tp. Cho mt

th khng nh hng G ,mt node c bit s c gi l ngun v mt nt t c gi l

ch th qu trnh tnh ton xc nh v tr lu lng da vo cng thc sau:

Trong k l nhng vn v lu lng ca mng , fi,jk l lu lng tng ng vi k

da vo arc(i , j) , ui,j , uki,j l cc s dng ch tng dung lng ca arc(i ,j) v dung lng

tng ng vi k , Fk tng cc lung lu lng ngang qua mng tng ng vi k . Nh vy

tng dng lu lng tng ng vi nhng vn lu lng mng k l:

y l phng trnh tuyn tnh c th gii bng phng php LP ( tham kho

Okam83)


35/89

Mt th thch y l s tng tc xy ra gia hai cng vic trn ( thit kt LSP v

xc nh lu lng) . Khi mt khong cch nht nh mt LSP thit lp . Th mt ti u

ton cc c gng tch hp thit kt LSP v nh v lu lng nhng phng php ny phc

tp. Trong khi mt ti u cc b th chia thnh hai phase ring.

7.6 Cu hnh li kin trc o ng quangTrong chng 5 ta tm hiu vic cu hnh li mng WDM , tip theo ta xem xt vic

xy dng vic nh x a ch IP da trn cc ng quang WDM trn nhiu hop. Mt ci

tin ca mng WDM l tit kim chi ph c th h tr nhiu vng hot ng nh . C

ngha l nhiu lin kt vi cc a ch IP khc nhau s c truyn ng thi trn cng

mt ng vt l l si quang v cc lin kt o IP s c nh tuyn thng qua nhiu

hop chuyn mch WDM.

Hnh 7.9 ch r l mt thit k cu trc o v nh tuyn mng IP thng qua vic cu

hnh li mng WDM. C ba thnh phn trong mng:

- nh tuyn lu lng

- Thit k cu trc IP

- nh tuyn ng quang.

Hnh 7.9 Thit k v nh tuyn topo o


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nh tuyn lu lng l chuyn cc gi tin i ng ng nh tuyn v d dng giao

thc OSPF c gii thiu trong chng 2 v chng 3 . Thit k kin trc IP l ch

chnh trong phn ny . nh tuyn ng quang l cung cp mt nh x t cu trc IP o

sang cu trc mng WDM vt l . nh tuyn ng quang bao gm hai thit b: chn lu

ng quang v ch nh bc sng m c tho lun trong chng 4 v chng 6 .

Trong phn tng kt , nh tuyn ng quang c th c tm tt thnh hai vn sau:

nh tuyn ng quang tnh: nh tuyn c tnh ton trc v lu trong bng

nh tuyn ng quang . S thay i lun phin cc ng cho mi ng quang s cp

cng c tnh ton v lu tr , ch nh bc sng l iu khin bc sng dng ti d

liu trn ng quang theo yu cu. Phng on l mt phng php n gin c s

dng trong vic ch nh bc sng. Ch nh bc sng l vic chn la bc sng ngu

nhin ph hp vi bc sng knh truyn.

nh tuyn ng quang thch ng: S dng thut ton nh tuyn ngn ng

SPF( Short Path First) cho nh tuyn ng i m n yu cu trng thi lin kt s phn

tn thng tin do s hin din ca trng thi lin kt c s d liu ni ti , do vic ch

nh bc sng tr nn linh hot hn i vi gii thut phng on phi da vo ti , tnh

hu dng nht v n khp nht kt ni tc d liu trn knh bc sng.

Thit k cu trc mng IP v nh tuyn ng quang c iu khin bi mt phngchc nng trong khi nh tuyn lu lng ch l mt thnh phn chuyn tip cc gi

d liu cng nh l nh tuyn gi.

C nh tuyn ng quang v thit k cu trc o c iu khin bi mt phng

chc nng , hai thnh phn hoc s dng kt ni khng m bo hoc l s dng couple

khng m bo. Mt gii php m bo vic bao ph k thut lu lng trong mng

IP/WDM l tch hp . Trong mt ng dng k thut lu lng c lp , nh tuyn ng

quang khng i c th l mt cng c s dng cho thut ton thit k cu trc mng .

Cch ny m bo rng kin trc thit k thc hin di lp mng WDM .

Mt mng IP bao ph ln mng WDM , lp server nh l mt nh cung cp truyn

ti dch v m ph v cho mt mng a dch v khch hng nh l mng khch hng

VPN, theo tin trnh mt khch hng ti mt dch v truyn ti lp IP t mng WDM .

Trong vic chp nhn v dch v , cc khch hng s c cp mt IP nh tuyn c nh

trc tip truy nhp vo mng WDM . Lp mng WDM cung cp kt ni ng quang giacc router ny . Tuy nhin khng ging nh kt ni cc ng dy thu bao ring trong

mng VPN ngy nay th s sp xp kt ni cc ng quang khng c nh . Trong khi


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tng cc ng quang kt ni c th l c nh hay b gii hn. Mi mt ng quang c

th kt ni n mt cp khc nhau ca cc router trong yu cu p ng vic thay i lu

lng trng thi ng. Yu cu ny c thut ton thit k cu trc o thc hin ti lp

IP . y cu trc o bao gm cc node v cc lin kt . Cc node l cc router v cc lin

kt l cc ng quang trong mng WDM.

Trong phn tip theo chng ta s tnh ton vn u tin v kho st mt s vn

tip theo . Chng ta s trnh by gii thut phng on ti u mng thng qua khong

cch .

7.6.1 Cu trc o bnh thng v bt bnh thng

Cu trc bnh thng l cu trc vi nhng nh ngha r rng v s kt hp kt ni

gia cc nt . Cu trnh khng bnh thng l cu trc da trn trng thi ng ti u

mng da vo khong cch. Vic qun l v nh tuyn trong cu trc bnh thng c

thc hin d dng nhng vic thm vo hay xa mt node trong mng c thc hin kh

khn v d cu trc bnh thng bao gm:

Ring (vng)

Shuffle-Net

MSN (Manhattan Street Network) GEMNet

HyperCube( siu lp phng)

De Briujn Graph

Nhng cu bnh thng thng nh tuyn chm phc tp v i xng nhng c kh

khn trong vic xc nh s lng b pht yu cu trn node , linh hot v s sai lch li .

V d mt cu trc siu lp phng bao gm n dy vi s node yu cu N th b pht yu

cu (n-1)lognN trn node vi trung bnh khong cch cc hop l lognN v ng knh

mng l lognN . So snh vi mt cu trc MSN ch yu cu hai b pht trn node nhng

khong cch trung bnh gia hai hop v ng knh mng yu cu l Cu hnh

Shuffle Net cng cho khong cch trung bnh gia cc hop nh hn cu trc MSN . N

c nhiu ng thay i t mt node u cui n mt node u cui . Tuy nhin n cn

nhiu b pht trn node l n . Trong phn tip theo ta s tm hiu v cu trc khng bnhthng.


38/89

7.6.2 Trnh by vn thit kt cu trc mng

Trong thit k cu trc mng o c th thc hin da vo cc i tng khc nhau ,

m i tng ch yu quyt nh qun tr. C hai loi i tng c bn chn la :

Mt l cc ng dng c tnh nh hng , cc ng dng ny th lin quan n vn QoS

ti mi ng dng nh l tr t u cui n u cui . Mt vn khc l mng nh

hng lin quan n vn mc s dng ti nguyn mng nh l trn .

u vo ca cu trc mng bao gm ma trn lu lng yu cu . Cho mt mng IP

vi N router , ma trn lu lng yu cu NXN , T(i , j) l mt lung lu lng kt hp ( s

bits/s) t router i n router j . Cc gi tr ny c la chn bng k thut tin on chc

chn da trn vic o lng ban u . Chung ta xt k thut tin on lu lng trong mt

phn khc, trong phn ny ch yu l tm hiu thit k cu trc mng .V vy vic xc nh

mt ma trn lu lng yu cu T (i ,j) bng cch o lu lng t router i n router j trnmt ca s iu khin thi gian . Thut ton thit k cu trc mng s dng cng c phn

mm xc nh bng cho lung lu lng IP yu cu.

iu kin khi u lin quan n thut ton ti u v cc i tng . Thut ton thit

k cu trc mng c hai li khi u: loi th nht l thng s cm nhn t mng nh l

trng thi ti ng lin kt nh l mt iu kin khi u chc chn cho thch ng t

ng . Loi th hai l cc quyt nh qun l t bn ngoi mng trong trng hp s dng

thut ton cung cp cho vic thit k cu trc mng . Theo Rama96 thit k cu trc

mng o v nh tuyn c tnh bng phng trnh MILP ( Mix integer Linear Program )

lm nh nht kh nng nghn ln nht trn bt k lin kt ca cu trc mng o ti mt

mc chc chn vi tr khng i . Cng thc ny c th c vit di dng :

Cl l gi tr lu lng trn lin kt l ( s gi truyn trn l) . Ti u ha phng trnh

MILP vi nhng vi nhng rng buc sau:

iu kin rng bc bc node cu trc o: vec t bc node D c n phn t , mi

phn t di vi mi i thuc N l mt bc node ca router i.

Rng buc lin tc bc sng: Trong sut qu trnh nh tuyn ng quang , kh

nng thiu bc sng chuyn i trn u ra chuyn n cng hin ti rng buc tnh lintc bc sng. Mt chuyn mch ch c th h tr mt nhm cc cng kt ni tng ng

vi cc bc sng . Do khng th thay i cc cng vi bc sng khc .


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Tr gii hn: Ti mi cp node mng thi gian tr hu nh l bi s ca thi gian

tr cc ng ngn nht trong cu trc vt l.

Cu trc si vt l v iu kin rng buc sn sng bc sng: nh tuyn ng

quang da trn cu trc si vt l v tnh sn sng ca knh quang.

Cng thc MILP trn l mc tiu cho vic ti u ton cc cho bt k iu kinrng buc tr no . N bao gm thit k cu trc o v nh tuyn ng quang . Sau phn

ny chng ta s trnh by vic thit kt cu trc o . Xem xt vic ly tnh nghn lin kt

n nh l s khi u cho thut ton thit kt cu trc ch ng. y c khong cch

nghn v thi gian nghn c nh ngha do ngi s dng . Ch rng thut ton cu

hnh li ch c tc dng khi ti nguyn mng cha dng , trong trng hp ny cu hnh li

ch sp xp li ti nguyn mng mt cch tt hn . Nu mt mng qu ti ton cc cu

hnh li mng o trn cng mt cu trc mng WDM khng c tc dng . y khi thm

vo nghn , iu kin khi u to ra s phn tn trong phn phi ti.

7.6.3 Cc thut ton heuristic

K t khi MILP tnh ton phc tp th vic thit k cu trc mng da vo thut ton

heuristic . Ci tin ca phng php ny da vo thut ton ti u chnh xc thit k

cu trc o mt cch linh hot .

Kho st thut ton thit k cu trc ng quang:

Heuristic c ba thut ton sau: Thut ton thit k cu trc heuteristic HTDA , thut

ton thit k cu trc logic tr nh nht MLDA, thut ton thit k cu trc logic c lp

lu lng TILDA. HTDA to ra mt ng quang gia hai node gim lu lng yu

cu . Ti bc node mng mt ng quang mng truyn lu lng yu cu. X l ny

vn c thc hin tip tc cho n khi lu lng trong mng khng cn nhiu . Nu tt

c lu lng yu cu c xc nh , phn cn li ti nguyn mng c la chn ngunhin t ng quang cho n khi ti nguyn c s dng ht . tng pha sau ca

heuristic l n gin cho qua trnh nh tuyn ti mt hop tip theo . MLDA thit lp mt

ng quang gia hai node k nhau v cui cng HTDA p dng xc nh phn cn li

ca ti nguyn mng vi iu kin rng buc . MLDA tht s l mt thut ton m rng

ca HTDA trong trng hp bc mng logic cao hn bc mng vt l . TILDA pht l i

lu lng yu cu hon thnh nhng mc tiu ca n l lm nh nht s lng bc sng

c s dng.TILDA u tin c cu trc l mt tng ng vi to ng quang u tin

ca hop v cui cng l cu trc hai- nhiu ng quang cho hop. Thut ton heuristic tip

tc thit lp ng quang cho n khi iu kin rng buc xut hin .


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Vo [Bane 97] hai heuristic c xut: LP da trn s lu lng ln nht mt

hop OHTMS v loi b lin kt thng qua s tng hp LEMS . OHTMS tng t nh

HTDA to ra tng lu lng ln nht ti mt hop trong khi vn di tr kt ni ca cu trc

o. LEMS u tin to ra mt kt ni cu trc o y bao gm tt c cc node trong cu

trc vt l . Khi lng ca bin c thit lp cng vi lu lng yu cu ca chng v

lu lng cp nht v c lng li. V qu trnh x l tip tc thc hin cho n khi gii

hn iu kin rng buc xy ra.

Thut ton heuristic thit k cu trcc cy :

Thut ton ny c nh ngha nh sau:

Cu trc ng quang ti mc IP c xc nh: trong N l tp hp cc

router , L l tp hp cc lin kt IP , n=|N| v l=|L| . Vi N, ni l ch s router . Mt lin kt

IP lun c kt ni 02 hng v vy hai ng quang n hng trong lp mng WDM

l dng ca mt lin kt o ti lp IP. Vi L, l i,j ch s lin cc lin kt , lij-c bng thng lin

kt , y lij-c=lji-c=max(lij-c, lji-c) .

Vecto bc node D c n phn t , mi phn t d i vi mi i thuc N l bc node ca

router i. V l=1/2idi cho bt k cu trc o IP no.

Ma trn yu cu lu lng: xc nh bng T, T l ma trn n hng , n ct , trong

T(i ,j) 0 vi mi i , j thuc N l gi tr lu lng trong n v thi gian t router i n

router j .

Lng lng X l mt ma trn nxn trong X(i, j) l gi tr lu lng (n bits)

truyn t router i n router j trong mt khong thi gian chc chn.

Thut ton s dng cc k hiu sau:

Ma trn yu cu lu lng d Tr=T-X

Mt vec t lu lng Fc cu to t ma trn T theo hai bc:

- Ma trn i xng ca T l Ts : T=Ts=max{T(i, j), T(j, i) } vi mi i, j thuc N

- Phn loi phn tam gic pha trn ca ma trn Ts gim to ra vec t F .

Vec t lu lng ti hop Fh c xc nh: {F(i, j)xH(i , j)} vi mi i , j thuc N ,

H(i ,j) ch khong cch t node i n node j .

Ma trn kt ni G c s dng trnh by th tng ng vi cu trc o IP ,

ma trn G l mt ma trn c n hng, n ct , mi phn t G(i , j) c gi tr bng 1 khi c khi


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c kt ni gia router i v router j ngc li G(i, j) =0 . Do ma trn G c gi l ma

trn i xng.

Lu lng tiu chun:

Khong cch hop ti trng trung bnh:

Vi iu kin rng buc :

V

li lu lng tiu chun:

li khong cach hop ti trng trung bnh:

y hnew v new l khong cch hop ti trng trung bnh v lu lng chun cho cu

trc mi cn hold, old l khong cch hop ti trng trung bnh v lu lng chun cho cu

trc c hoc cu trc c nh.

Mc ch ca thut ton heuristic l thit k cu trc ng quang v to bc nodevt l ca mi node mng . Cu trc u ra cho php cc ng song song gia cc i

ging nhau ca cc node. Mt kt ni ng quang l song cng . Mt heuristic bt u

vi mt th gm n node c lp tng ng vi n router . Nhng heuristic c cng pha

u tin s to ra cu trc cy bao ph kt ni nh nh c cung cp. MaxT(i , j) c

cung cp cho cu trc cy metric. th khi ng kt ni t c bng cch lp li vec

to lu lng F m n c lu li gim ti yu cu , mi F(i) tng ng vi T s(p,q) .

Mt kt ni c thit lp gia router p v router q khi khng c ng gia hai router

ny. Khi mt cu trc c n node mng th s c n-1 kt ni khi ng.


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Thut ton heuristic yu cu cn li (RD):

Bc 1: Cu trc mt cy span cung cp mt khi to kt ni cng vi vec t

lu lng F vi iu kin rng buc gim bc node . Khi F c lu gim bc theo

yu cu , khi to kt ni cy c cu trc theo dng lu lng yu cu ngay mt

hop k cn . Khng c kt ni song song cho cc cp ging nhau gia cc nodes .

Mi kt ni s dng bng thng ln nht c xc nh bi matran L.

Bc 2: p dng lu lng yu cu vo cu trc cha hon chnh . Hai phng

php xc nh lu lng c xem xt. Phng php u tin s dng nh tuyn

ng ngn nht truyn thng v d s dng SPF .Mt phng php khc l p

dng SPF v k thut sai lch mt dng lu lng

Bc 3: Khi cha c giao tip c ch nh ging nh cha c yu cu c h

tr trong cu trc cha hon chnh. V vy to ra mt vec to lu lng mi s dng

ma trn d tha cn li . Vec to lu lng mi ny c lu lm gim bc ca yu

cu cn d.

Bc 4 : Tm thng qua mt vec to lu lng mi tm mt lung lu lng mi

m mt kt ni c ch nh gia hai im u cui. Chn kt ni mi ny vo

cu trc v t kt ni vi bng thng ln nht theo ma trn F. Cui cng quay tr

li bc hai. Thut ton dng khi khng cn tm ra c kt ni mi.

Bc 5: Nu s giao tip ri khng nh hn 2 th p dng hi t heuristic trn.

Thut ton RDHP ( Residual Demand Hop Count Heuristic algorithm) bao gm 04

bc:

Bc 1: Cu trc mt cy span khi ng cung cp kt ni gia cc node cng

vi vec t lu lng F ging bc 1 trong RD.

Bc 2: p dng lu lng yu cu trong cu trc cha hon chnh , ging bc 2

trong RD.

Bc 3: Tnh ton khong cch hop gia cc cp ca cc node da trn cu trc

cha hon chnh.

Bc 4 : To ra mt vec to lu lng mi s dng ma trn d ca mi phn t ti

trng bng m hop ca n . Vec to lu lng mi c lu gim bc ca m hopyu cu cn d . Tm dc theo vec t lu lng tm mt lung lu lng m kt

ni c ch nh gia cc im u cui vi bng thng ln nht ca n tng ng


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vi ma trn F . Cui cng quay li bc 2 v gii thut ch dng khi cn mt kt

ni mi no thit lp .Nu s giao tip khng nh hn 2 th p dng iu kin hi tu

heuristic trn.

Thut ton DHP( Demand hop-count Product heuristic algorithm)

Bao gm 5 bc: Bc 1: ging bc 1 trong RD

Bc 2: Tnh ton /tnh ton li khong cch gia tt c cc cp node da vo cu

trc khng hon chnh.

Bc 3. To vec to lu lng mi gim bc s dng ma trn cn d m mi phn

t l mt trng s tnh ton ti hop.

Bc 4: Tm dc theo lu lng vecto hop tm mt lung lu lng m ti

mt kt ni mi c ch nh gia cc u cui . Chn thm mt kt ni mi vo

trong cu trc v t kt ni vi mc bng thng ti a. Cui cng quay li thc

hin bc hai.

5. Gii thut ch dng khi khng c mt kt ni mi no thc hin . Nu s giao

tip rnh khng nh hn 2 th p dng iu kin hi t heuristic nh trn.

Heuristic hi t:

Bc 1:Ch s node vi nhiu giao tip IP m

Bc 2: p dng lu lng yu cu vo tng phn ca cu trc hon chnh.

Bc 3: Phn loi tt c cc kt ni da vo mc s dng ti nguyn trong gim

bc . Kt ni mc s dng c t cao hn lin kt mc s dng ca hai lin kt

m to thnh cu trc kt ni. Bc 4: Chn kt ni ti nh nht m khng phi mt khong cch n node vi

cc giao tip m t danh sch phn loi . Ngt kt ni ny to hai kt ni mi tng

cp tng ng vi hai giao tip m tn ti .Hai kt ni giao tip m ny l kt qu

ca vic ngt kt ni ti nh nht.

Bc 5: Quay tr li bc hai nu s giao tip m ln hn hoc bng 2.

7.6.4 S chuyn cu trc o

Trong mt m hnh mng IP ph ln mt mng WDM cu hnh li , IP v WDM giao

tip vi nhau thng qua giao din quan UNI hay WDM NC& M( Chng 5) . UNI quang


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cho php mt s thng tin cu trc ca mng vt l (v dng cu hnh mng WDM v kt

ni) chia ti vi mng khch hng . y ta gi nh bao ph ln cu hnh li mng l

mt mng vt l WDM c th h tr cu trc o . Nu mt cu trc o khng h tr hoc

ng quang khng th thit lp do iu rng buc lp mng WDM , mt gii php a ra

l di chuyn tr li cu trc ban u ca mng . Mt nghin cu gn y ch ra rng hin

tng nghn c chai trong mng IP/WDM thng xay ra ti cc giao tip IP hn l ti cc

giao tip mng WDM. Cc giao tip IP th t v khan him hn cc giao tip WDM .

Nhn chung c mt s giao tip WDM ri . V th nu mt cu trc o khng th h tr

bi mt nh cung cp ( v d nh cung cp mng server) , cc nh cung cp nn xem xt

kh nng cp nht dung lng ca mng . Cc nh thit k c th tun theo vic chia s

thng tin cu trc vi khch hng . Thit k cu trc heuristic v s di chuyn heuristic

c trnh by trong nhng phn ring. Nhng gi nh chung l m hnh bao ph IP ln

m hnh mng cu hnh li WDM h tr cu trc o.

iu kin rng buc mng WDM vt l ng trong sut qua trnh cu hnh li tch

hp IP/WDM v d trong m hnh ngang hng IP bao ph ln mng WDM cu hnh li ,

thng tin cu trc mng WDM chia s vi mng IP . Vic thc hin tch hp IP/WDM l

mt kh nng chin lc . Ngay khi thut ton thit cu trc ch ngh cu trc o linh

hot. Tuy nhin iu ny i hi mc chnh xc v nh hng thng tin cu trc sn

sng ti c s d liu ca mt router ni ti. Trong mt mi trng mng phn phi v

mi trng thi gian thc , th thng tin cu trc ni khng th cp nht theo ngy v tnh

hi t mng trong p ng v d thay i trng thi lin kt c th thc hin trong nhiu

ln . Thm vo thng tin mng WDM n mng IP khng th phn theo t l nhn t

quan im iu khin mng. Cu trc IP ph ln mng chuyn mch gi WDM c xem

xt trong phn sau ca chng ny.

Thm ch nu ti nguyn lp WDM h tr s di chuyn tun t ca hu ht ccyu cu v d nh khi thm vo tt c cc kt ni mi trong khi cha ngt mt kt ni c

no . K t khi cu hnh li mng WDM ln dung lng ln (OC-192) thay i ti nguyn

hiu qu cho vic kt ni lung lu lng ngi dng u cui . Th tc di chuyn bao

gm tun t thit lp v phn chia vo cc ng quang mng WDM . Lung lu lng

cp nht n cc ng quang thay i sau mi bc di chuyn. Ph thuc vo cu trc

mng ko theo vic nh tuyn mng to ra hiu qu cho u cui ngi dng. T khi

cu trc li ng quang c xem nh l cu trc ng quang thay i ti lp IP , giao

thc nh tuyn IP phi cp nht s thay i ny . Khi cu trc thay i d dng trong vic


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truyn vng chuyn tip vi cc giao thc nh tuyn tn ti , lu lng ngi s dng

trong sut qu trnh nh tuyn hi t sau mi ln cu hnh li.

Cc gii thut lp lch di chuyn ti u th phc tp do c nhiu thnh phn hot

ng . Thut ton di chuyn heuristic lam gia tng tnh di chuyn cu trc ng quang

trong IP/WDM.

Thut ton heuristic di chuyn cu trc:

C bn hot ng ban u cho thc hin di chuyn nh sau:

Hot ng A: Di chuyn mt bin :

Cu hnh IP ca hai router tng ng xung

Ngt kt ni hai ng quang n hng trong lp mng WDM

Cp nht log file cho vic di chuyn bin ( nh chi tit cc ng quang, cc giao

tip khch hng, tn/a ch WADM, s hop trung bnh , WSXC, chi tit v router v cc

bc sng)

Hot ng B thm mt bin:

Tnh ton v thit lp ng lin kt o trong lp mng WDM . Ch mt lin kt

o IP thc hin s dng hai ng quang n m cho php hai si quang ging nhau

nhng bc sng knh quang khc nhau. Nu li xy ra th chuyn sang hot ng R.

Cu hnh a ch IP ti giao tip router cp nht a ch IP . Ch s dng giao tip

khng nh s hay ch nh trc ca nhiu IP th cp v mt IP s cp .

Cp nht log file cho bin chn vo .

Hot ng E: c lng kt ni mng

Kt ni y bt u mt node n bt k cc node khc trong mng bng cch

s dng tm ng su .

Tr li 0 nu mng ngt kt ni v 1 nu mng kt ni y .

Hot ng R: Lu li cu trc gc

V d s di chuyn b li

Da vo log file tng bc tng bc ngt ra/thit lp cc ng quang cu trgc/c c lu li

Gi bn tin li v thng bo n nh qun l hoc khch hng.


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Thut ton heuristic gia tng di chuyn cu hnh mng bao gm cc bc:

Bc 1 : Cu trc hai hng: ri hng v xp li hng bng vic so snh cu trc

c/mi . Ri hng bao gm cc bin c xa ri lu vo gim bc ca ti bin .

Danh sch xp li hng c thm vo. Khi to log fiel gi du vt cu cc

bin thm vo/xa .

Bc 2: iu khin mt khi to xa bng cch chn hai bin t ri hng . Nu kt

qu mt bin xa tng ng vi ngt mt kt ni ( da vo hot ng E) th bin

c b . Nu tt c cc bin ri hng nguyn nhn gy ra ngt kt ni mng th t

nht hai bin ti c chn . Cc bin c chn la c xa s dng hot ng

A v xa t ri hng.

Bc 3: C gng thm bin t s xp li hng nu iu rng buc v bc sng v

giao tip c tha mn. Hng c tm thng qua tt c cc bin c thm vo .

Mt bin c thm vo s dng hot ng B v xa t vic xp li hng.

Bc 4: Tm thng qua vic ri hng v xc nh bin m ti t nht nhng khng

lm ngt kt ni mng . Xoa bin v xa n t ri hng.

Bc 5: Tr li bc 3 v bc 4 cho n khi vic ri hng v xp vo hng khng

cn na.

7.7 Cu hnh li cho mng chuyn mch gi WDM

Mng chuyn mch gi WDM vn cn trong qu trnh nghin cu, nhng h thng

chuyn mch gi quang lng t xut hin. Khng c nghi ng g khi h thng ny s

chia s tng ng vi cc mng chuyn mch gi khc, chng hn nh cc router. Tuy

nhin, nhng gi d liu quang c nhng nh dng mo u khc, n tng t nh nhn

header trong MPLS. Ngoi ra, h thng chuyn mch gi quang yu cu mt kch thc

gi ln so vi lu lng ngi dng c h tr bi router IP in. Chc chn, iu ny

c th thay i khi h thng chuyn mch quang tip tc pht trin. V d, chuyn mch

quang c th chuyn i nhanh chng sang chuyn mch gi v s xut hin ca b nh

quang hc.

7.7.1 Tng quan v cu hnh li chuyn mch gi WDM

Nh chng minh trong cc mng IP, cn phi c h tr ca cc gi tin cng nh

cc mch in t trong mng chuyn mch gi. Mt mng chuyn mch quang IP c th

c m hnh trong bt k bc sng no trn mt si quang trong lp WDM c th c

t ng thit lp ch gi hoc ch mch. Trong ch gi tin, chuyn mch nhn


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quang (OLS) lm vic nh MPLS nhng l trong min quang. Trong ch mch, OLS

lm vic nh mt mng chuyn mch thng thng, i hi mt tn hiu bo hiu trong

cc knh thng tin.

Hnh 7.10 Cu hnh li mng chuyn mch gi WDM

Hnh 7.10 cho thy cu hnh cho mt mng chuyn mch gi WDM. Nh trong hnh,

c mt topo IP/OLS c tch hp, trn c c cc ng dn quang v cc chuyn

mch MPLS LSPs (Label Switched Path). Cu hnh OLS cp n cu hnh ng dn

quang v cu hnh MPLS LSP. giai on hin nay, cc mng khng OLS h tr y

IP ch cho vic chuyn tip.V d trong mt phng d liu, cc OLSR khng c cng khng hiu r tiu IP

datagram. Trong phn nyvic cu hnh li cc thut ton s nghin cu trong lp IP cng

nh tho lun cc lp trong WDM. Thut ton l ph hp nht vi nhng mng tch hp

IP / WDM, ni m mt giao thc IP- c s dng iu khin cc mng vt l.

Tt c cc phn t mng c nhn thc IP. a ch IP c gn cho giao din

chuyn mach / nh tuyn. Mt trng thi lin kt giao thc nh tuyn IP, v d nh OSPFvinhng phn m rng thch hp, c s dng cho cc phn t mng khm ph cc

topo vt l. Cc bc sng trong mt si c kim sot bng cch s dng mt c ch


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da trn MPLS ( v nh vic la chn bc sng cc b). Thng tin v kt ni ng

quang v phng thc hot ng ca tng bc sng ca tt c cc loi si cng c trao

i thng qua phn m rng OSPF. Mi phn r duy tr hai mng topo mng. Mt l topo

vt l m t cc yu t mng vt l v cc kt ni si gia chng, mt l topo lightpath,

c nh ngha bi cc kt ni ng quang. Khi mt phn t mng quyt nh

thit lp mt kt ni lightpath mi, u cui ca lightpath chu trch nhim nh tuyn cho

cc lightpath thng qua tp vt l ty thuc s cho php ca mng. Khi mt nt ngun

mun gi d liu n mt nt ch, c hoc khng tn ti mt ng ni quang trc tip

gia hai node. Hn na, thit lp mt ng quang mi c th c hoc khng do s sn c

knh bc sng v cc hn ch khc. Trong cc chuyn mch MPLS in thng thng,

cc LSP l cc knh o do o chng c th c thit lp h tr ngay c nhng kt ni

mng li . Do d liu, chuyn mch nhn ti MPLS c th c gi trong mt LSP

hop

Vi kt ni dng li khng y OLS, d liu nh tuyn l cn thit mi

phn t mng v cc khng gian nh tuyn tng ng l mt topo ng quang. Do ,

c hai lp nh tuyn. Kin trc lp ny l kt qu t nhin ca mt m hnh gi (IP) trong

mt chuyn mch ton cu. Do , k thut lu lng c th c thc hin ti mi lp.

Trong khi lp cao hn, v d nh topo ng quang, lu lng MPLS ang nghin cu

v ng dng. Cc lp thp hn cn mt thut ton mi cu hnh a ch v cu hnh li

ng quang trong topo vt l ca mng WDM. Ngoi ra, n cng l cn thit tng

tc phi hp hot ng k thut lu lng gia lp trn v di. C hai cch tip cn

thit lp mt ng dn mi, trong c th l ng quang (lightpath) hoc LSP. Theo

phng php tip cn u tin, bt c khi no mt node cn phi thit lp mt LSP ti nt

khc, nt u c gng thit lp mt lightpath trc tip n nt cui. Nu lp vt l

khng th h tr lightpath ny, nt u c gng nh tuyn cc LSP thng qua cc topo

lightpath hin hnh, tc l thit lp mt LSP in.

Nu thit lp qu di , cu hnh li cho lightpath c gi. Cch tip cn th hai c

xu hng tn dng ngun ti nguyn WDM c cu hnh trc khi thm vo nhng

b sung. Khi mt nt c cn thit lp mt LSP ti nt khc, nt u lun c gng nh

tuyn LSP thng qua topology lightpath hin hnh, tc l thit lp mt LSP in. Nu iu

ny tht bi, nt cui u c gng thit lp mt lightpath trc tip n nt cui ui, tc

l thit lp mt LSP quang. Nu khng thnh cng, cu hnh li lightpath c kch hot.

iu th v l cng mt lightpath ci t v cu hnh li cc thut ton c th c s

dng trong c hai phng php tip cn. tng c bn l con ng ngn nht nh


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tuyn qua cc i tng topo vt l c rng buc nh bc sng, s lin tc bc sng v

cht lng tn hiu ca knh.

7.7.2 iu kin cu hnh li

K thut lu lng MPLS c bn c th c p dng cho cc cu hnh li LSP trong

lp trn. Khi mt router bin li vo cn thit lp mt LSP cho mt router bin li ra, ccLSP s c tnh ton trong topo cn li t c bng cch p dng tt c cc hn ch p

dng vo topology lightpath. Nu LSP mi yu cu t bng thng B nht nh, topo cn

li c th c ly t cc topo lightpath trong lin kt vi bng thng sn c t hn B

c loi b. Theo topology cn d, mt con ng ngn nht t router bin ngr vo ti

router bin i ra c th c xc nh. Ni chung, con ng ny khc vi ng i ngn

nht gia cc cp cng mt router tm thy trong cc topo lightpath. Cc tn hiu MPLS c

ch m bo vic thit lp ng dn c tm thy dc theo cc nt trung gian. Bngcch kt hp hn ch da trn nh tuyn v thit lp ng dn r rng, MPLS n

mc ny c th khai thc cng sut gia mt cp node ln n gii hn quy nh gia

hai nt. Sau khi im cc i LSPs t c yu cu c nu ra nhiu hn t mp cng

thm nhp vo b nh tuyn router cng mt cnh i ra, mt trong hai hnh ng c th

c thc hin:

Hnh ng 1: Mt s LSPs hin hu mun c u tin tng dung lng trn ntc chai thch ng vi LSPs mi, chng cn phi c mt u tin ci t cao hn.

Hnh ng 2: Yu cu thit lp LSP mi khng c chp thun.

n mt mc nht nh, trng hp u tin c th c coi l mt vn c th

hn ch vn nh tuyn, trong khi trng hp th hai ch n gin cho thy cn bng ti

MPLS t n gii hn ca n. Trong trng hp ny, ng c nh tuyn ti cc b

nh tuyn bin vo cho thy t topology cn li mt th b ngt ni vi t nht hai

thnh phn. Cc router bin ng vo thuc v mt thnh phn v router bin ng ra thuc

thnh phn khc. Khng nh cc LSP t c do u tin, nu khng c WDM trn si

lin kt, cc LSPs mi s chc chn b chn.

Trong cng ngh WDM hin ti, cn c mt tng k thut lu lng m li ln lp

trn LSP. K t khi topology lightpath b gom bi cc kt ni knh vt l l cu hnh li,

c th tn ti mt topology lightpath trong hai thnh phn b ngt kt ni trong topo d

c th c kt ni li. Topo lightpath mi ny ti mi thi im phi tho mn cc yu

cu kt ni cho tt c cc LSPs hin ti. Thut ton cu hnh li heuristic c thit k

khm ph nh mt topology lightpath c trnh by trong phn sau.


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7.7.3 Mt trng hp nghin cu

Trc khi trnh by cc thut ton heuristic, chng ta s dng mt v d minh ha

cho tng c bn ng sau thut ton. Hnh 7.11(a) s a ra cc v d mng WDM vi

mt topo vng ring 6-node. Trong hnh, cc ng xm m l cc si cp hin ti, mi

si h tr hai bc sng. Cc ng chm i din cho cc kt ni lightpath qua cc nt.

Mu sc khc nhau ch ra cc bc sng khc nhau. Hnh 7.11(b) cho thy topo lightpath

tng ng.

Hnh 7.11 S dng cu hnh li ng quang iu tit nhiu LSP

Ti mt thi im nt C cn thit lp mt LSP mi ti nt F, v topo lightpath d

phng nt C nhn thy khi c gng thit lp cc LSP mi c th hin trong hnh 7.11

(c). R rng, cc ngun lc hin ang c sn node C khng h tr cc LSP va

c yu cu. By gi cu hi t ra l liu n c th cu hnh li mt s cc lightpaths

thch ng vi LSP mi. Cu tr li l c th. Tuy nhin, mt cu tr li xc nh ch l mt

vi bc i th nghim. Cc th nghim u tin l xem nu mt gii php cu hnh li

c th kt ni hai thnh phn b ngt kt ni li vi nhau. Cc th nghim tip theo l liu

tt c cc LSPs hin ti b nh hng cng vi va c yu cu c th thch nghi bi cc

gii php cu hnh li. Trong v d ny, mt gii php (cng l gii php duy nht) c th

vt qua c th u tin l cu hnh li kt ni lightpath gia nt B v nt D. Mt

tnh nng quan trng c lin quan ca lightpath ny l im kt thc ca n thuc v mt

trong nhng thnh phn v qu o vt l ca lightpath i qua cc thnh phn khc. Do

, mt gii php kh thi l cu hnh li 'ph' cc lightpath trong thnh phn th hai.


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Mt c th chn ph v lightpath ti F nt nn hng quang BD ngun s tr thnh hai

hng quang BF v FD. Sau , topo cn li sau khi lightpath cu hnh li tr nn nhng

g c th hin trong hnh 7,11 (d).

Cc tc ng trn tt c cc LSPs hin gii thiu cu hnh li ny l ti thiu. c

bit, ch c s dng LSPs lightpath BD trc khi cu hnh li cc tip xc vi tc ng

hn ch. Sau khi cu hnh li, mt trong s cc LSPs s lan truyn ti mt hoc nhiu hop

c cp bi cc LSPs khng tn ti bng cc con ng khc nhau. Hn na, c kh

nng l cc LSPs hin ti s li trn con ng ban u ca n, m bo vt qua th

nghim th hai. By gi thit lp l va c yu cu LSP gia nt C v nt F n gin.

V d ny c tnh b qua cc s trc tip ca cc LSPs v li ch ca s n gin. i trc

tip vo ti khon s khng thay i bt k kt lun c thc hin trong v d.

7.7.4 7.7.4 M t thut ton Heuristic

Thut ton c cc nh ngha sau y:

Cc topo vt l ca mt mng quang WDM G k hiu l< N, F>, trong N l tp

cc nt mng v F l tp cc kt ni si. Mt kt ni si A l mt cp lin kt si ch

hng ngc nhau gia hai nt mng.

Topo ng quang P nhng trong topo vt l c k hiu l < N, L>, trong L

l tp hp cc ng quang. ng quang l mt knh quang hng bt u t nt u

ca mng, i qua khng hoc nhiu cc nt mng khc v kt thc ti nt cui ca. V vy,

qu o ca mt ng quang c th c biu din nh l mt chui cc si lin kt v /

hoc mt danh sch cc nt mng.

Vic nhng mt topo ng quang vo topo vt l c gi l lp bn ca topo

ng quang. Vic lp bn lin kt mi ng quang trong topo ng quang vi mt

danh sch cc nt mng l vic ng quang duyt qua trong topo vt l.

Thut ton ny s dng cc k hiu sau y:

Topo ng quang d tha (hoc mt topo n) R (A,Z) l mt tim nng u cui,

A< N, mt khc na s c thit lp LSP vi u cui Z


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topo ng quang cn d, R (A, Z) lun lun p ng hu ht tim nng u A, n thuc

v mt thnh phn c gi l k hiu l thnh phn u C_A, v tim nng cui Z, thuc

v mt thnh phn khc gi l thnh phn ui k hiu C_Z.

Q l mt vng loi ng quang LSP-c trng. N ch ra cc kh khn ang khi

nh tuyn cc LSP thng qua cc topo ng quang hin hnh. Khi thit lp mt LSP n

Z, A p t Q ln P c c R(A,Z), tc l R(A,Z) l mt th con ca P thu c bi

R(A,Z)=Q*P. c im k thut v trnh by mt vng loi khng trnh by y.

Cc thut ton heuristic c mt phin bn c bn l s dng khi mt nt mng n

khng xc nh v tr ngun cha mt LSP mi, v mt phin bn m rng cho php

gii quyt cng mt vn cho nhiu nt mng khi mt s iu kin c p ng.

Thut ton heuristic da trn b sau y:

B : Cho mt topo vt l G, mt

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Dich Chuong 7 IP WDM